MUSEUM OF COMPARATIVE ZOOLOGY. 275 
PLATE IV. 
In none of the figures are the vitelline cells and the nuclei of the thin epiblastic 
layer of the primitive hydrophyllium brought out with sufficient distinctness. There 
should be two layers instead of one at pyf. in Figs. 1, 2, and 3. 
In Figs. 2 and 4 the wall of c. p. 7. is too black, and does not show the thickness 
of the hypoblast. The rows of nematocysts on the surface of hyph., Fig. 8, 
are not well shown. The clusters of nematocysts at the margin of Ayph. after the 
bifurcation of ¢b. are faulty. The cilia on the surface of the ovum, well seen in 
Fig. 2 at pyt. in my drawing, are not found in the photographic reproduction. 
Fig. 1. A larva (primitive larva) in about the same age as the last and in a like 
position, except that the primitive covering-scale or hydrophyllium is 
turned a little more to the plane of the observer. 
** 2. The same, looking through the primitive covering-scale upon the apex of 
the float, which lies in the geometric centre of the figure. Three days 
old. 
** 3. Older larva, free-hand drawing, showing growth of serrated scale (ser. 
hyph.). 
‘< 4, The same, lateral view. 
“* 5-7. Successive stages, in reduction in size of the primitive hydrophyllium, 
following its great development. 
*« 8. A larval Agalma, one week old, bearing a large flat hydrophyllium (rem- 
nant of the primitive covering-scale) through which runs a tube (¢0.) 
which bifurcates and ends at the distal edge in clusters of nema 
tocysts. 
