I have found the following pictures representing cysticercoids of Eucestoda.
If I correctly understand the right part of the picture, I would say that the development of the scolex is portrayed on the right, as the formation of what I think to be two acetabula shows. Nevertheless, with respect to the images on the left, it is totally unclear to me, since the text says nothing about it, what the structure that seems to be encapsulating the animal is.
I know that cysticercoids develops from an oncosphere, but I do not know whether that sort of capsule that seems to be enveloping the animal is a part of what was the oncosphere's tegument -the embrionophore- that it can have gone out of and is entering again...
Does anybody reading this question know more about it? I thank you very much for any answer!