Jumping right in with your organic intersections, your work here is largely coming along quite well. You've drawn the individual sausages with a lot of focus on how they slump and sag over one another, conveying a good sense of the gravity in the scene. Your cast shadows are also demonstrating a keen sense of how those forms relate to one another in space (and how the surfaces curve towards or away from one another). For the most part you're also fairly consistent with your cast shadows' directions, but I did notice that in this one, the leftmost sausage of the three is casting a shadow slightly to the left, whereas the one on the far right is casting more to the right.

Moving onto your animal constructions, by and large your work here is excellent. There are a few things I want to call your attention to, in order to help you continue to get the most out of these exercises, but as a whole I'm very pleased with what I'm seeing, especially in regards to the general respect you have for how each form you add exists in 3D space. There are a few places where you slip back into working on two dimensions instead (which I'll address), but by and large, your constructions each feel quite solid and sturdy, rather than just feeling like a collection of lines on a flat page.

So, to that point, there are some spots where you take shortcuts. For example, on this duck there's a bump around its forehead area, as well as the bump along the base of its throat and the back of its neck, which were added as partial (flat) shapes, rather than complete forms that wrap around the existing structure. That relates back to the point about not altering silhouettes from my critique of your lesson 4 work.

One area where a similar issue comes up that you might not expect it, however, is how when we add fur, we can end up deviating too much from our existing structure, and add flat shapes like this inadvertently. As shown here, when drawing the crest of that bird, you ended up leaving gaps between your phases of construction of an arbitrary nature - this results in a weaker structural relationship between the steps. Always break down your constructions into small steps, and avoid adding more complexity than what's already present can support. Also note how I added the core structure of the crest as another solid, enclosed form, with an intersection between it and the main head mass clearly defined.

Now, another thing that can contribute to this kind of issue is the tendency to increase the thickness of our lines as we move through the stages of construction. This is something we see quite a bit in your work. If we take a look at this fish for example, you started your construction faintly, and then gradually built up more thickness with each passing stage. This also resulted in you tracing back over many existing sections of linework, rather than allowing them to stand for themselves, as it can be tempting to try and bring everything back up to a similar level of thickness, creating a clear separation between the sketch (treating it like an unnecessary underdrawing) and the "clean-up pass".

For what we're doing here, we do want to be drawing our linework with a more similar line thickness throughout, up until the end of the construction phase. Then we can go back over it, adding line weight to key, specific, localized areas to help clarify how different forms overlap one another, as shown here. This line weight does not follow the silhouette of the overall object - it follows the silhouette of each individual form, and should not jump from one to the next (as this can cause the "bridging" effect I called out on the back of the bird's neck). When we let our line weight jump from one form to another, it's a lot like we're pulling a sock or stocking over our object, smoothing everything out just a little bit too much, and robbing it of its subtler elements.

The last thing I wanted to call out is just a reminder about how we need to focus on the silhouette of our additional masses, and the specific way in which they're shaped. 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.

As shown on this horse, be careful with where you put your corners. Corners, along with inward curves, are forms of complexity that should only occur in response to other forms pressing up against them. Where that complexity is placed matters a great deal.

Lastly, I know that you were having some trouble with heads (specifically those facing forwards) by your own account, but I'm honestly not concerned about that at all. The way you handled the front-facing stag shows a lot of attention being paid to how the complex head structure is divided into planes, and how the different pieces fit together. This follows the spirit of this head construction demo from the informal demos page - so I assume you did see it (though you don't explicitly apply it directly to your drawings), but if you haven't, do be sure to give it a read.

Anyway, as a whole I do still think that you're progressing really well, and that your constructions are quite strong. I'll go ahead and mark this lesson as complete - I believe you should be well equipped t o apply the points I raised here on your own.