This lesson (and those preceding it) gives students a lot of tools to employ to help build up complex objects from simple pieces to yield an end result that maintains the illusion of solidity - and as a whole, you are using most of them, and from the looks of it, using many of them quite correctly. You're using simple core forms to establish the major masses, you're employing the sausage method to build out the legs while maintaining a sense of fluidity to those limbs, and you're using additional masses - not perfectly - but not poorly either.

There is however a key problem that is getting in the way of these tools working at their best - from what I can see, it seems you're not investing as much time into actually observing your reference image. As discussed here back in Lesson 2, we need to get into the habit of observing our references not only carefully, but also frequently - looking away only long enough to transfer very specific pieces of information into our drawing. When it comes to construction, we observe our reference to identify every individual form we wish to draw, to figure out how it should be oriented, what kinds of proportions we need to maintain, and so on.

Construction itself requires a good deal of thought, and even once we have that form identified, we need to think about how it relates to the other forms around it, and how they're all meant to fit together. As we drift to focus more on that, it is not uncommon that we forget to look at our reference as often as we should, and without realizing it we end up relying much more on memory. Memory of course is flawed, and as humans we're not particularly good at recalling large amounts of very specific information. Instead, our brain tosses most of that out, focusing on the major notes. Piecing together a believable construction from that results in something far cartoonier and oversimplified. Combining that with a well developing grasp of spatial reasoning and construction, you end up creating animals that are kind of half there, but kind of goofy looking in most cases.

So as far as that goes, the answer is simple: you need to spend a lot more time observing your reference. Slow down the process, and really allow yourself to identify the specific nature of the information/forms you want to transfer over to your drawing. Don't trust your memory, don't allow yourself to jump right into the next form. Always go back to the reference, and refresh your memory. Focus particularly on proportions, on determining how the different forms relate to one another in space.

As far as the bodies go, I'd say that the hippo on this page shows the strongest observation - although the lower jaw definitely gets drastically oversimplified. It seems that when you face more complex spatial problems, you get a little overwhelmed, and your response to that is to observe less, and instead to "wing it" based on what you know. That's a common reaction, and instead you need to get used to taking a step back and taking stock of the situation.

Now, with that addressed - and I really do feel that a greater investment in observation will yield enormous improvement - there are a few other things I want to point out.

• For head construction, it does seem to me that you're familiar with the explanation on the informal demos page. One thing to note there is how the eye sockets tend to have a pentagram shape, with the flat edge along the top and the point along the bottom. This creates an excellent wedge in which the muzzle form can fit, and provides a straight base upon which the brow ridge can sit as well. I noticed in a few cases you flipped that eye socket upside down, which definitely caused problems.

• When drawing feet, don't just draw them as flat 2D shapes (even if they're seen largely from the side, we're always going to be able to see more than one orthographic plane of the form, so make sure you're shaping that silhouette to properly imply a 3D form. Also, don't use lines to separate the toes - actually construct the toes onto the foot form. You likely ended up going for simple lines as you did because the foot to begin with was a flat shape, rather than a form of its own. Often times these kinds of little mistakes can snowball by changing how we perceive our own drawing. If we continually reinforce the idea that everything's 3D, then we will be continually encouraged to keep that going (especially when we start believing in the illusion we're creating).

• Don't forget to add a contour line at the joints between your sausage forms. You do this sometimes, but other times you let it slip.

• Remember that when drawing your eyes, you've placed a ball in the socket, and are now wrapping eyelid forms around it. It's not just a matter of drawing a symbol of an eye, - the eyelids themselves are three dimensional forms that interact with the ball form, and they extend beyond the ball itself.

• Open mouths can definitely be tricky - don't be afraid to break the upper and lower jaw into separate forms, in order to keep your constructional steps simple. Also, keep breaking those steps down into individual forms. For example, hippo jaws tend to have protrusions along the sides - like little chunks where the big fangs sit, leading to a sort of hammer-head shape to the end of their muzzles. You can always build that up by adding additional boxes to the ends there.

• You're moving in the right direction when drawing those additional masses along the legs, and along the animals' backs. Just be sure that you really push the impression of how they "grip" the body, especially on the torso. Instead of having the forms sit gently atop their spines, wrap them around so they actually press up against the big shoulder/hip masses, curving their silhouettes to accommodate them.

Here are some redline notes on that hippo construction to illustrate most of the points above.

In order to give you the opportunity to apply the points I've raised above - especially focusing on a more direct and continuous observation and study of your reference, I'm going to assign some additional pages below.