As a whole, I think you've definitely shown a great deal of growth and improvement over the course of this lesson. It's very clear that you approached the homework in a way that focused very much on learning from what you were doing, analyzing what worked, what you understood, and digging into the things that you weren't confident in. As a result, there were definitely areas with mistakes, and I will call them out, but many of these are areas where you definitely figured things out by the end.

I'm going to break down this critique into three major sections, just to keep things organized.

To start, head construction. Here I'm really happy you delved so deeply into that informal demo - it demonstrates the process and thinking I'm going to be basing any future video content on, once my overhaul of the course gets this far. In these breakdowns you've shown a pretty strong grasp of how that approach allows us to keep all the different parts of the head - the eye socket, the cheek, the brow ridge, the muzzle - wedged up against one another in a way that establishes strong spatial relationships between them.

Now this was something you didn't employ for your birds, and as a result the eye sockets ended up floating more loosely, and not feeling as securely grounded in the constructions. You applied the process everywhere else however, and that's great to see. I would however put a bit more emphasis on the specific shape of the eye sockets. With the otters, for instance, the angle at which the bottom part of the eye socket cuts downwards also influences how the muzzle ends up being constructed, as shown here. Making it a sharper angle, and pulling it downwards, can help avoid the sense that the muzzle is being pulled flat against the cranial ball. In the otters' situation it's clear that you were aiming to have a bit more of a smushed muzzle, but I think it went a little overboard.

Also, remember that eyeballs are big - we only see a portion of them, the rest is hidden behind the eyelids. You appear to be trying to draw the eyelids such that the whole circle representing the eyeball is visible, but this is incorrect.

Next, use of additional masses. Here I can see you wrapping those masses well around a number of different aspects of your constructions, but there are still some places where the silhouette of the given mass is not drawn with enough consideration towards how it is meant to wrap around the existing structure, and how it is meant to actually fit together with whatever other masses might be present (like the big shoulder and hip masses that help drive the legs). Here's an example of what I mean. In these cases, it seems like your additional masses take on a bit more of an arbitrary shape, which suggests you're not entirely aware of how those silhouettes should be designed.

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.

One thing you should avoid when it comes to these additional masses is relying too much on addiitonal contour lines - that is, the ones you tend to slap on top of the ones that don't feel quite as solid. I know it's tempting, but contour lines in this case are only going to make that form feel 3D in isolation - they won't define how that form relates to the existing structure. When you then go on to add contour lines, you somewhat impede your ability to learn from the mistake that was made in shaping the form's silhouette - because it still ends up feeling 3D, it feels like you may have "saved" the drawing. Instead, you should put yourself in a position to see those mistakes clearly, and to deal with their source, rather than doing what you can to make the drawing look good. These are exercises, after all, and the point is to learn from them.

The last major section is leg construction, and here you're mostly doing a good job. I noticed that in some spots - like your hybrid's legs, you neglected to add the contour lines that define the joint between your sausage segments - this is a very important step, so make sure you don't skip it in the future.

Your use of additional masses in these cases is coming along well, although it definitely can be pushed even further. There are a number of cases - like your first llama - where the legs mainly stick to fairly simple sausage structures. Paying closer attention to your reference images to find all the stuff that's going on, as shown here with this dog leg, is a great way to push your constructions farther.

Aside from those major sections, the only other thing I wanted to talk about was texture. I felt that the alligator tail texture you built out came out quite nicely. When it comes to the octopus tentacles however, specifically the suckers that don't break the silhouette of the tentacle, remember the textural principles from lesson 2. That is, not necessarily constructing every textural form, but rather trying to imply its presence through the use of cast shadows.

Anyway, all in all you've done quite well and have shown a great deal of growth. I'll go ahead and mark this lesson as complete.