STINGING-CELLS IN CEASPEDOTE MEDUSA. 



771 



these showed the same orientation of nematocysts as in the 

 specimen figured by the Hertwigs. I have figured one of 

 these sections (Text-fig. 3) chosen from a series in the Cam- 

 bridge Morphological Laboratory; comparison with that of 

 Moerisia (Text-fig. 1) is very instructive. 



Text-fig. 3. 



orel.--- 



- -TLem. 



A longitudinal section through the base of a tentacle of Car- 

 marina sp. vel. Yelnm. «ei».. Neniatocyst migrating through 

 the ectoderm of the tentacle. 



Gunther's figure of Limnocnida {7, fig. 6) shows that a 

 similar migration of thread-cells must occur in that medusa. 



4. The Development op the Medusa of Mceeisia. 



As shown above, the nematocysts of the main stinging- 

 batteries of Moerisia are formed in two quite distinct positions 

 in the medusa : (a) The manubrial endoderm, (6) the ecto- 

 derm of the ocellar bulbs. 



In order to properly understand the origin of these 



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