168 



H. M. FUCHS. 



a somewhat later larva in lateral optical section. The larva is more 

 elongated and the apical patch has become diffuse, without any long 

 cilia. The buccal aperture is seen to be strongly ciliated. Fig. 6 is a 



Fig. 6. — Larva of Glycera. 3 days. 

 From the dorsal aspect, an. — Anus. 



trochophore of three days old. Little weight can, however, be attached 

 to the ages of the larvie, as in the same culture some larvte, probably 

 those which have developed from more mature eggs, will grow much 

 more rapidly than others. At this stage the gut has thick walls, and 

 there is a constriction between the stomach and intestine, which is 

 much more evident than in later larval life. A very light green 

 pigment is scattered over the surface. The apical patch seems to con- 

 tain a pair of vibratile organs (Fig. 7), the significance of which is 

 unknown. 



Fig. 7. — Larva of Glycera. 4 days. 

 From the ventral aspect, an. — Anus. vi. — Mouth. 



Fig. 8 shows the typical shape of this larva. The upper hemisphere 

 is rather more conical and less dome-shaped than the lower. This is 

 the reverse of the condition in a typical trochophore. Large and granular 

 green pigment corpuscles are scattered over the surface. They are 



