MAYER: STAUROCEPHALUS GREGARICUS. 7 



Kleinenberg's hsematoxylin, and appear to be filled with a mass of 

 deeply stained granules that may represent the coagulum of some fluid. 

 Figures of these cells, in older larvse, are shown in(gl) Figures 7, 8, 

 Plate 1. I believe them to be glands, and they are probably homologous 

 with the "frontal bodies" found by "Wilson ('92, p. 421) in the larva of 

 Nereis, and perhaps also with the " problematic bodies " observed by 

 Mead ('97, p. 256) in the larva of Amphitrite. Malaquin ('93, p. 395, 

 Plate XIV., Figures 12-10) has also found glands in a similar position 

 in the head of the larva of Autolytus Edwarsi. 



Figure 15, Plate 2, represents a larva 3^ days old, and Figure 7, 

 Plate 1, shows a dorso-ventral section of the same. The eyes are now 

 quite large, and the green patch representing the gland cells is very 

 prominent. There are now three bands of cilia : a broad oral band, 

 a narrow post-oral, and an anal band. Two sets of setie, consisting 

 each of thi-ee bristles, have made their appearance immediately posterior 

 to the post-oral l:)and of cilia. These setoe originate in folds of the 

 hypodermis. A longitudinal dorso-ventral section (Figure 7) of the 

 worm in this stage shows the very large gland cells ((//) of the head. 

 The mouth (ni) shows signs of being about to break through, although 

 as yet it is not functional. The same may perhaps be said of the anus 

 (an). The mid gut (st) of the woi-m now consists of a delicate ento- 

 dermal epithelium enclosing a mass of highly vacuolated cells laden with 

 yolk spheres. 



Figure 16, Plate 2, shows a larva 5h days old, and Figure 17 illus- 

 trates the character of the setse from the same worm. Most dorsal 

 of all there is a single long seta (Figure 17, b) and immediately be- 

 low this there are two sette of the sort shown in Figure 17, a. 



Figure 18, Plate 3, shows a larva 10 days old. The worm is now 

 0.5 mm. in length, and possesses three sets of sette. Until the end of 

 the 15th day the larvse are remarkable for exhibiting a strongly posi- 

 tive phototaxis. They swim through the water at all depths, but 

 large numbers of them are sure to be found clustered together in 

 those parts of the aquaria where the light is strongest. 



At the end of the loth day the cilia disappear, and the worms cease 

 to swim through the water, and sink to the bottom. Figures 19, 20, 

 represent a young worm that is 16 days old, and Figure 8, Plate 1, 

 shows a dorso-ventral longitudinal section of the same. There are 

 now four pairs of parapodia provided with dorsal and ventral cirri. 

 A number of sensory hairs are found scattered over the prrestomium, 

 and the posterior segment of the body exhibits a pair of dorsal cirri. 



I 



