DEVELOPMENT OF EGG FRAGMENTS IN CEREBRATULUS. 125 



Perfect pilidia 30 { ^""^ } ........... 5-7 per cent. 



Defective pilidia 5 ............................................ 14.3 per cent. 



It is striking that comparatively few larvae turned out to be 

 defective. All of these are shown in Fig. I, C-G, 1 a glance at 

 which shows that they are certainly abnormal, yet their defect is 

 not so great as those obtained at later periods (Series B and C). 



FIG. i. 



i C represents a larva which would be perfect, if there were an 

 apical organ. \D is another defective one with three apical 

 organs, two tufts having been about to fuse ; in other respects it is 

 perfect. A pilidium represented in \E is much more abnormal 

 than the preceding two. It has two apical organs and a pair of 

 ciliated lappets of smaller size. The shape of the gut also is not 

 normal. Another pilidium (i/ 7 ) resembles the one with three 

 apical organs just described (i-D), but differs from it in having 

 three apical organs widely separated from one another --two on 

 the left side, one on the right. In this larva the left ciliated lobe 

 is indented. Lastly we have a very defective pilidium (i G), 

 which, like i C, has no apical organ. While the ciliated lobes 



1 All the figures throughout the paper have been drawn by the camera ; 84 

 diameters magnification. 



