I know Haeckel was into drawing natural structures, not just actual beasties, but what does the thing in the bottom-right corner have to do with arachnids? Is it an organ? An egg? A cluster of eggs?
Also, can anyone give me a reason for the existence of the pattern on the abdomen of the spider at the bottom (which I’ve also seen in the live version). It’s like a cross between a cone shell and a tabby cat. Is it some kind of camouflage?