Starting with your organic intersections, you've done a great job with these, specifically in establishing how these forms interact with one another in 3D space, slumping and sagging under the weight of gravity. Your use of cast shadows is coming along as well, although I did notice a spot where the cast shadow should have sunk in between the forms beneath as shown here.

Continuing onto your animal constructions, as a whole your work here is coming along well, and I can see clear signs that you're developing a good understanding of many of the concepts at play here, but there are some areas where I feel like I can clarify some things to yield yet better results. Overall though, I do feel your grasp of 3D space, and how these forms relate to one another within it, is coming along well.

The first thing I want to discuss comes down to your use of additional masses.

Here I can see that you're definitely thinking about how to design the parts of the silhouettes that make contact with the existing structure, capturing how they wrap around that structure. There are however two issues that I'm noticing.

The first has to do with the part of these forms' silhouettes that don't make contact with anything - these end up featuring complexity that doesn't align with the fact that nothing is actually pressing up against them.

One thing that helps with the shape here is to think about how the mass would behave when existing first in the void of empty space, on its own. It all comes down to the silhouette of the mass - here, with nothing else to touch it, our mass would exist like a soft ball of meat or clay, made up only of outward curves. A simple circle for a silhouette.

Then, as it presses against an existing structure, the silhouette starts to get more complex. It forms inward curves wherever it makes contact, responding directly to the forms that are present. The silhouette is never random, of course - always changing in response to clear, defined structure. You can see this demonstrated in this diagram.

So the key thing to avoid is any sort of complexity - that is, inward curves - where there's nothing to actually cause it. If we look at this cat, you'll see where I changed an inward curve along the top to an outward curve. Along the back, as well, it wouldn't hurt to extend the mass a little so we can press up against the hip mass, defining further relationships between the different components of the structure.

The other issue with the additional masses is just the tendency to add contour lines to them. In the majority of cases, they actually don't need them. Through mindful design of the silhouette of each mass, you can usually convey as much volume for those forms as is needed. They don't need the additional contour lines, although I think there's a tendency to draw those contour lines a little too wide even when you do which throws things off.

In the cat example for instance, the cat is pretty much moving across our field of view from left to right - so the contour lines themselves should be much narrower. Remember that the degree of a contour line helps convey its orientation in space. When they're wider, it suggests that they're turning towards the viewer, whereas here we want them to run across the field of view. It wouldn't be completely narrow, but it would be fairly close.

The next topic I wanted to discuss was line weight.

Throughout your constructions, I noticed the tendency to start out with lighter lines for your earlier phases of construction, and darker lines later on. While as a whole you aren't going back over all of your linework, I definitely noticed that you were tracking back over some sections (tracing back over linework usually creates hesitant marks, introducing wobbling which can flatten things out due to the erratic increase in complexity).

In general, try to keep the thickness of your lines consistent throughout the process. Once you're done with the construction, you can jump in and add further line weight to help clarify how certain forms overlap one another, but the key point to keep in mind here is that line weight should only be applied in specific, localized areas - the ones where those overlaps occur. Don't go back over long sections of line, and be sure to apply that line weight using the ghosting method to ensure that the marks are still confidently drawn. Here's an example of two overlapping leaves to illustrate what I mean by keeping it in localized areas.

Next, let's look at your leg construction.

Here I can see some variation - sometimes you adhere more closely to the sausage method introduced in Lesson 4, but other times you get a little more relaxed. For example, one common thing I see is that you aren't entirely consistent in defining the joints between sausage sections with contour lines as shown in the diagram, and often you'll add contour lines elsewhere along the length of the sausages. I actually address this in the diagram as well, stating that you should not be placing them along the sausage's lengths - only at the joints.

The reason for this is that the contour lines that define intersections and relationships between forms in 3D space are simply vastly more impactful than those that sit along the surface of a single form. In general, whenever you add a contour line that sits on a single form's surface, you should probably have a conscious, solid reason for doing so, rather than applying them "just because".

Lastly, let's look at how you approach your head construction.

As Drawabox is continually evolving as a course, the way I approach explaining certain concepts change, mainly as I get more experience in explaining them. One such case is with head construction, where a while back I ended up adding a little disclaimer at the top of the tiger head demo pointing students to this section of the informal demos page as the most "current" and clear explanation of how to tackle the construction of heads. Eventually it'll be incorporated into the main lesson material (once my overhaul of the whole course reaches this point), but that'll be a ways off.

I strongly recommend that you look at that explanation if you haven't already. It explains how head construction is all about ensuring that all the different parts of the head - the eye socket, the muzzle, etc. fit together like a three dimensional puzzle. Even the shape of the eye socket leans into this, with the shape shown there allowing space for the muzzle to be wedged in between, along with a flat surface for the brow ridge to rest across up top.

Based on your drawings, I feel you may have missed this, as you still have the elements of your animals' heads floating more loosely relative to one another. For comparison's sake, here's how I would tackle a rhino's head.

In addition to this, another point that can help when it comes to understanding how the eye lids actually wrap around the eye ball (often students will just draw a simple iconic eye shape and leave it at that), is to think of the eyelids as being separate additional masses of their own, as shown here.

In conclusion, I've laid out a number of things for you to work on, but as a whole I do feel you're doing a good job. There's a lot here to absorb, and I strongly recommend that you read through my feedback several times over a period of time. All the same, I do feel confident in marking this lesson as complete, and letting you move on. I'll leave it up to you to apply my feedback in your own drawings.