42 JOURNAL OF THE 



The development of the afferent system in Chalinula was 

 not worked ont with certainty. 



The embryology of the preceding sponges in which a 

 rhagon type is developed agrees pretty well with onr gen- 

 eral notions of sponge phylogeny. Bnt there are other 

 sponges, the development of which has been so excessively 

 modified as no longer to be of any nse as finger posts to 

 phylogeny, bnt which afford an excellent field for the study 

 of what may be called the methods of coenogeny. In 

 //ah'sarca Dujarc//;2n{MQtschmkoff, I. <r.), for instance, there 

 is a solid larva in which the canals appear as so many 

 separate lacunae surrounded by parenchyma (mes-entoderm) 

 cells. The canals only subsequently acquire a connection 

 with each other. In Esperia* the subdermal spaces, canals 

 and chambers arise separately as lacunae in the parenchyma. 

 The chambers are formed from aggregations of small cells 

 in the parenchyma, which Maas believes, on wdiat seems to 

 me insufficient evidence, to be ectoderm cells of the larva 

 that have migrated into the interior. The efferent canals, 

 Maas thinks, are formed from similar cells. In Esperia, 

 according to Yves Delage,t the chambers arise by division 

 of special mesoderm cells. The epithelium of the canals 

 comes from the larval ectoderm, which has migrated into 

 the interior. In Spongilla, according to the same author, J 

 the ectoderm cells of the larva are engulfed by mesoderm 

 cells and then become the lining cells of the flagellated 

 chambers. The observations of Delage on these points 

 need to be confirmed before they can be taken as the basis 

 for generalizations. 



In vouncr Stellettas^ the subdermal cavities seem to arise 



*Maas. Die Metamorphose von Ksperia Lorenzi, etc., Mith. aus dem Zool. Sta. zu 

 Neapel, Bd. lo, Kept. 3. 

 tSur le developpement des Kponges siliceuses, etc. Coinptes rendu.s. T. no. 

 JSur le developpement des Eponges (Spongilla fluviatili.s). Comptes rendu.s. T. 113. 

 gSollas. Challenger Report on Tetractinellidae, pp. XVI, XVII. 



