I'm glad you're starting to feel like the purpose of constructional drawing is clicking for you. I think there are definitely major elements of your work that have come along quite well, though there are definitely areas in which things can be improved.

Starting with your organic intersections, your work here is coming along pretty well, though I am noticing places where some of the sausage forms are actually infringing upon the volumes of others. For example, if you look here, that sausage has entirely given up the integrity of its own form to meld over the one below it. This is actually in a way a good way to exercise for certain challenges within this lesson, but as far as this exercise goes, you should focus on maintaining the integrity of each form, trying to keep their sausage-like volumes while they wrap around the underlying structures. Similarly, here we can see where it looks almost as though the bottom sausage has actually cut into the top one, which isn't what we're after. We need that top sausage to actually react, by the sausage as a whole wrapping around the one underneath.

One of your strongest overall constructions is definitely the hedge sparrow. Specifically, you've done an excellent job with it in building the structure out of simple forms, of establishing how those forms relate to one another in space, and of drawing through all of those forms. I'm also pleased with how you approached the eye - big socket drawn with separate strokes, big eyeball, and eyelids wrapping around it. When it comes to eyesockets in other drawings, I felt that you were skipping into the habit of trying to draw them with a single continuous stroke instead - this suggests an element of rushing or sloppiness where you forgot the importance of thinking through every straight edge that makes up that socket's footprint.

I think as you try to continue making sense of the techniques and of the animals' bodies as a whole, your work does take a bit of a dip in quality (especially as you move through the wolves), but as you progress it starts to pick up again with a definite confidence that comes from having better understood how you were employing the techniques. Setting texture/detail aside and focusing purely on construction was a very good move. It's something I often tell students to do when they're getting distracted by texture, and I think it had a good impact.

All that said, I think there are definitely still some issues that need to be sorted out. Here are some notes on your first grizzlybear. Along its back, you drew the "additional masses" incorrectly - you didn't draw each as an independent, enclosed form. This is important to better grasp how all these forms relate to one another in space. You also didn't establish how those forms wrap around or integrate with other volumes within the existing structure. Even if you're piling a mass on top of another mass, they still need to interact with one another. Each one is an addition to the world, and they exist there as a solid, concrete element.

Lastly, I think that while you were focusing more and more on construction, your attention to your reference tended to drop a fair bit. While construction is how we interpret and apply what we see, we still need to make sure that we're studying our reference images closely in order to identify how big things need to be, how different elements relate to one another in space, and so on. If we try to rely on our memories, things tend to come out oversimplified, or disproportioned. The head of this bear, for example, came out very small.

Another issue that I attempted to talk about in that redline image but that is more easily visible in this wolf is how you're putting very large, long additional masses along the animals' backs to bulk them up. Try and think in terms of each mass representing a muscle group. We get a lot of the nuance and subtle elements of the animal's silhouette from how our additional masses interact with one another - by trying to capture too much in a single additional mass, things end up too smooth and even, and we lose a lot of the subtler interactions between forms.

On this bear, we see that issue of trying to do too much with a single additional form (along the back) again. Also, another issue that stands out is how you're bulking up the legs. Instead of adding a ball/circle, and then trying to bridge them across, every single addition should be some sort of an organic form that wraps around the underlying structure, as shown here.

I feel like when you get down to your second bison, you start to show a better grasp of how to approach building up additional masses. I'm pleased with the progress it shows. That said, there is still one last major issue that I want to point out: you tend to use way too many contour lines.

Contour lines suffer from diminishing returns - one may be helpful, a second much less so, and a third even less than that. When students pile them onto their drawings where they don't contribute much, it shows that the student isn't necessarily thinking about the specific task they want the mark to perform, and instead put marks down instinctually because they feel like that's what they should be doing. Instead, you need to always weigh the specific purpose you have for a given mark, to think about how it can perform that job best, and whether or not another mark might do it better.

There are multiple kinds of contour lines as well. There are the kines that sit along the surface of a single form, as they were first introduced in Lesson 2, but there are also the lines that define the relationships between forms (intersection contour lines). These intersection lines are infinitely more effective than the previous kind, and will have a far greater effect. That is why we reinforce the joint between sausage forms with a single contour line, and are not to add any additional contour lines along the length of the sausage forms. This was mentioned in the instructions for the use of this technique, but I do notice you still adding them here and there.

Now, I've outlined a number of things for you to keep in mind here, so I'll end off my critique here. I think you're making considerable progress and I'm thrilled to see your growth. There is still room for improvement however, and as such I'm going to assign a few more pages below before we move on.