1886, | Embryology. 567 
cephalic ganglion. In the anterior part of the body, the mesoder- 
mal cells form a gelatinous connective’ tissue between the organs. 
The pedal gland is now very strongly developed; its secretion is 
poured out between the ectodermal cells, a special opening for it be- 
ingabsent. At the sides of the body, above the foot, a ciliated band 
is present, which marks the site where the branchiz will appear. 
At the level of the first dorsal fold, the eyes may be recognized. 
The larva now leaves the egg envelope and swims about by 
means of its velum, The calcareous spicules are still enclosed by 
their mother cells, but soon break through. After the lapse of 
to have become smaller than in the preceding stage; in young 
Chitons (probably a year old) it is still present, but in those 
somewhat larger it is absent; it is, therefore, an organ pertaining 
to the embryonic period. The cuticular thickenings which lie in 
the transverse dorsal furrows are the rudiments of the segmented 
shell, and in each furrow, beginning at its anterior border, small 
calcareous plates are formed. The eyes are heaps of pigment in 
the ectoderm, with a clear nucleus in the center, lying close to 
€ branchial nerves. In a fully developed young Chiton they 
and cinereus, but in olivaceus somewhat before it. 
Mantle nial is developed. The species investigated oY DE 
rn was F zulipa Linn., var. distans Lam. 
PP. 217-225, pl. II, 1885 
, 
‘H. 
Wis Leslie 
Studies from Biolog. Lab., Johns Hopkins University, 1 
~ 
SF 
