stolon formation in species op trypanosyllis. 435 
the points (ped.) at which the ectodermal epithelium is inter- 
rupted indicate the situations from which they were detached. 
But together with the extension of the proliferating cusliion 
Longitudinal section through posterior end of stock (T. crosslandi, 
-) showing an advanced stage of stolon formation. st\ st-. The 
two first formed stolons, lat. Latei'al pi-ocesses of last segment- 
bearing stolons. aL c'. Diverticulum of alimentary canal in dorsal- 
most stolon. an'. Position of anus. Other letters as above. X 70. 
there has been a change in its histological character. At the 
stage represented by figs. 3 :ind 4 the whole of the cushion is 
closely packed with me.soblastic cells. Here this character is 
