After looking through the revisions, I am seeing a push towards heavier marks for no apparent reason. I have a question. Are you using a different pen when executing these marks? If so, I'd suggest not to change pen unless you're using the brush pen for the cast shadows. If that's not the case however, keep in mind that as with all the tools we use here, those are tools best used towards specific goals. In most cases a drawing with no line weight would do just fine. From there, I would only apply it where clarification is required, as shown here. The last thing we want to do is treat it like a swiss army knife to solve problems it's not really meant to address.

For the most part, you're not working in 2 dimensions anymore and that's good. The way you're applying your additional masses is also moving in the right direction and I encourage you to push these forms even further. When it comes down to it, the way the silhouette is actually designed matters a lot. It helps to think about how this mass would exist on its own in the void of empty space. Think about a ball of clay existing on its own.

Then as it presses against an existing structure the silhouette of this form gets more complex, inward curves forming where it makes contact. The silhouette is never random of course, always responding to the form that's present as shown in this diagram.

Moving into your head constructions, I'm getting the impression that you may not be quite as familiar with the informal demos section so I do encourage you to look more into it. Looking at how you approached the bear's head here, I understand that it can be a bit difficult to fit into the head construction approach shown here, due to the underlying structure being obfuscated by the fur. The trick really comes down to making a number of smaller moves, one at a time, rather than trying to make a few big moves that capture a lot of things at once. For example, starting off with a smaller cranial ball allows us to start establishing structure, without being committed to a scale thay may not work properly. Drawing a huge cranial ball is a common mistake, resulting with the rest of the facial features being smushed down in comparison. Here is how that bear head could be constructed, based on the methods outlined in the lesson.

Onto the next point, I did notice a few things that came up that I didn't outline originally and that has to do with the tendency to draw the pelvis area too large. As seen in this diagram, the pelvis should take up about a quarter of the torso length, leaving some room unoccupied by any solid mass.

Lastly, remember to add contour curves along the joints when constructing your legs.

That about covers everything I have to say. Hopefully my explanations make sense and help steer you in the right direction moving forward. I trust that you'll be working on these on your own time so I'll be marking this as complete. Feel free to move onto the 250 cylinder challenge.