ON THE DEVELOPMENT OF LINGULA ANATINA. 49 



spindle bodies occurring first in more advanced larvse. The 

 early corpuscles measure 8 /-* in diameter ; they are much smaller 

 than those of the adult (16-20,«), although very much like 

 them in form. At the centre of the corpuscle there is a re- 

 latively large, compact and round nucleus. The later development 

 of the blood cells consists chiefly in the increase of the cyto- 

 plasm. The refractive, probably nutritive, granule found in the 

 adult corpuscle is not as yet visible. When blood corpuscles 

 are crowded together they present a light red color, as in the 

 adult. 



In life the corpuscles accumulate at the posterior end of the 

 body cavity, and I at first thought they were proliferated there. 

 Sections, however, showed clearly that in this region there is no 

 sign of the production of corpuscles. On the other hand, in 

 transverse sections of some larvse, a mass of polyhedral cells on 

 the ventral side of, and just posterior to, the ventral ganglion 

 was seen which insensibly passed over to the ordinary epithelial 

 cells of the peritoneum on one hand, and to the blood corpuscles 

 on the other. These cells gave every evidence of having been 

 produced from the peritoneum and of being in stages of transfor- 

 mation into blood corpuscles. Afterward I was able to observe 

 in a living larva of the 8 p. c. stage that the posterior face of the 

 ventral ganglion has a jagged appearance, as if from this region 

 the blood corpuscles had recently come off and that some cor- 

 puscles were still adhering (PI. VIL, Fig. 99, b.c.). 



In the larvae of the C p. c. stage a curious element is found 

 floating in the body cavity. It is not very common. It is a flat 

 disc of an irregular outline ; sometimes it assumes a crescent 

 shape ; sometimes a spindle shape. On the flat surface there are 

 jound about ten parallel depressions stopping short at the margin 



