THE DEVELOPMENT OF ASTERINA GIBBOSA. 353 
small cubical cells; the ectoderm is made up of exceedingly 
long and narrow cells bearing flagella, and the wall of the 
hydroceele of similar cells, but I could not make out any 
flagella there. Fig. 144 is taken from the posterior end of the 
animal on the right side; the form of the ectoderm cells is 
well seen, and one observes occasional goblet cells (god.) 
amongst them. The section goes through a peculiar patch of 
peritoneum, where the cells are actively engaged in budding 
off the ameebocytes which float in the celom. So far as I can 
make out, however, no cells are budded off at this stage into 
the blastoceele (i.e. the space between the ectoderm and the 
ceelomic wall), and the mesenchyme cells are as yet entirely 
undifferentiated. The characters of gut cells are shown in 
Pl. 26, fig. 126. Although this is taken from a larva in which 
the metamorphosis has commenced, yet the characters of these 
cells do not vary till the very close of the metamorphosis. 
They have the same general form as the ectoderm cells, but 
the bases of the latter are often contracted, and leave chinks 
between them, whereas the endoderm cells are closely apposed 
to one another. Fig. 126 also shows another point of interest: 
here and there a small round amcebocyte may be seen applied 
to the basal end of the gut cells, and one discovers amongst 
the latter also one or two rounded cells, thus suggesting that 
these amcebocytes may be able to pass between the gut cells 
like the lymph cells in the Vertebrate intestine. 
Plate 27, figs. 183—135, are three sections through the larval 
organ which have already been alluded to. It is to be noted 
that in this stage the adhesive disc has short cilia, just as See- 
liger (18) has described for the adhesive disc of Antedon. Where 
I have put ‘‘ nerv. Jarv.” a thin strand of pale fibrous matter is 
observable with the highest powers. This is the only trace I 
can discover of a larval nervous system, and I am not perfectly 
satisfied about it, since it does not take the yellowish-brown 
tone with osmic acid so characteristic of the adult nervous 
system. Should my interpretation of it be correct, the larval 
nervous system would consist of a layer of ‘ Punktsubstanz ” 
underlying the larval organ. 
