184 BULLETIJS OF THE 



special pigment spots of the head which are called ocelli. The original 

 "pigment dots" (k) lie in the third body segment. The point of separation 

 between the stomach and oesophagus is near the seventh and eighth body seg- 

 ments. The formerly enclosed anal ring of green color and tlie two regions 

 of green pigment on the last body segment have coalesced, so that the whole 

 terminal segment has the same yellow and green color as the head. The intes- 

 tine is slightly tortuous in its course, and is clearly differentiated from the 

 stomach. Scattered red pigment spots appear on the external body walls along 

 the dorsal and ventral median lines. 



The oldest worm in the series described above was raised from the youngest 

 through the successive stages mentioned. Although the larvae as a rule bear 

 confinement with little discomfort, I was never able to raise them into the 

 adult Nephthys. 



The identification of the larvae of a related species by Claparede and Metschni- 

 koff has been followed, since three forms of the larvae which are here figured will 

 be found to resemble " stages " which they have already represented. The old- 

 est larva which was studied is much more developed than the oldest which they 

 had, and approaches the adult form more closely, which seems to me to add new 

 evidence to confirm the identification which they made. Until, however, it is 

 raised into an adult, or the youngest is traced back to the mother through the 

 egg, the identification must be regarded as provisional. The homology of 

 the black spots originally found on the apex of the preeoral lobe, but now in 

 the fourth body segment, is doubtful. The theory that they are homologous 

 with the embryonic otoliths of Terebella, has little to recommend it. It is 

 not known whether they are lost in later growth in older larvae or not. 



Claparede and Metschnikoff speak of these " eye-spots " as eyes with lenses, 

 and the neighboring transparent " cells " as brain lobes. In the oldest larva 

 which they represent in their figures (PI. XIV. Fig. 3, c) these bodies are 

 situated in the head. In the oldest larva which is described in the present 

 paper, they lie in the fourth body segment. Similar bodies have been figured 

 by Bobretsky * in the larvae of Pholoe. 



The movement of the " eye-spots " from the head into the fourth body seg- 

 ment is probably brought about by the growth forward of the head and the 

 anterior body segments. The means by which this has been accomplished is 

 not, however, perfectly clear. 



* KB HCTOPIH PA3BHTIJI AHHEIH;i;B, PI. IX. Figs. 3, 4. The copy 

 of this paper which I have used is from Zapiski Kiefskavo Obshto Yestestvois- 

 pitatalyei. 



