270 BULLETIN OF THE 
even in this larva with air or gas. Below it is a mass of reddish pig- 
ment concentrated in a cluster. The size of this larva is about the 
same as that of the last. 
On August 13, seven days after the Agalma had been placed in the 
water, I was surprised to see, on looking for my larve through the walls 
of the glass vessel in which they were confined, that they had very 
much decreased in numbers. This led to the discovery that, whereas 
up to about this date they were found at all depths in the water, the 
larvee are now to be seen only upon the surface. They often cluster 
together there, and the size of the float imparts to them a silvery color, 
like a small bubble of air resting on the water. The reason why the 
larvee seek the surface at this phase of their development probably is, 
that the float has grown so large, or that the size of the primitive 
hydrophyllium has diminished. Whatever may be the cause which led 
the Agalmata to come to the surface, an effect which can probably be 
ascribed to the two causes mentioned above combined, we find that 
the size and general outlines of the first-formed covering-scale have 
undergone several modifications. Fig. 5, Pl. IV. shows a larval stage 
taken August 13th, in which the size of the scale is much smaller than 
in the larvee already described. It is found at this time in the life 
of the larva that the border of the covering-scale has a tendency 
to draw together, and its surface becomes grooved or furrowed. In 
Fig. 6 we see a continuation of the same process, and in Fig. 7 still more 
reduction in the size of this body. One or two structural features have 
led me to regard the flat angular body on the yolk of these larve as 
the primitive hydrophyllium reduced in size. The tube which is found 
in the primitive scale, especially at the marginal termination, has a yel- 
low color with black dots. These figments were found in the tube of 
the more reduced scale in its present condition. The small nuclei 
spread over the surface of the primitive hydrophyllium, called in our 
above description the nuclei of the epiblast, are easily recognized on the 
surface of the modified scale. With the reduction in external form 
of the plump walls of the first-formed scale, or primitive hydrophyllium, 
there has taken place also a change of form in its internal cavity. At 
the distal border of a scale represented in Pl. IV. fig. 8, the tube of the 
scale has bifurcated and extends in two divisions to the bell rim, where 
both end in the neighborhood of clusters of large nematocysts or lasso- 
cells. A yellow color was observed at these points, although the tube 
of the scale throughout most of its course is not as markedly colored. 
The small cell-like spots which appear on the surface of the scale and 
