146 Mr. W. S. Kent on the Embryology of SjJonges. 



of the sponge-product remain bound together in a social cluster 

 throughout their metamorphoses, in Salpingoeca they are scat- 

 tered abroad, as shown at PI. VI. fig. 26, during the imma- 

 ture or uniflagellate condition, their development to the adult 

 state being afterwards effected during an attached and solitary- 

 condition. The matured collar-bearing spongozoa next throw 

 around them, as already related, a common investing veil of 

 glairy sarcode or syncytium, while the solitary Salpingosca 

 builds for itself, by a similar process of exudation, its elegant- 

 shaped protective sheath or lorica* ; this at first is also soft and 

 syncytium-like, but acquires an apparently chitmous or perhaps 

 keratose consistence after short exposure to the water. The 

 sliglit distinction between the two forms under the conditions 

 last described finds its precise counterpart among the higher 

 ciliate Infusoria, as instanced by the solitary lorica-inhabiting 

 types Gothurnia or Vaginicola as compared with the social 

 genus Ophrydmm^ the innumerable units of which exude 

 around them and inhabit a common mucilaginous domicile. 

 The social slime-dwelling form, Phalansterium of Cienkowski 

 {Monas socialis, Fresenius), as compared Avith Bicosoeca or 

 other simple loricate Monadina, affords again a similar parallel 

 among the more closely related ordinary Flagellata. 



The further development to the characteristic adult sponge- 

 form of the attached ciliated gem mule, the collars and iiagella 

 of the individual units being withdrawn and replaced by an 

 investing syncytial mantle, has, as already mentioned, been 

 described by Mr. Carter, with relation more especially to the 

 siliceous-spiculed type Halichondria simulans, in this same 

 magazine for November 1874. Barrois, again (I.e.), has 

 traced these same developmental phases in a similar manner in 

 numerous other sponges, including more prominently Halisarca 

 lobularis and Desmacidon fruticosa. Among the phenomena 

 connected with this further development, attested to by both 

 these writers, is the early appearance of the spherical ciliate or 

 monad-lined chambers which have received from Mr. Carter 

 the title of ampullaceous sacs. How these chambers originate 

 does not appear to have attracted the attention it deserves. 

 Haeckel, hoAvever, has pronounced them to be mere spherical 

 dilatations of the ordinary canals, while Barrois maintains that 

 they make their appearance first as independent structures 

 within the substance of the syncytium, communicating with 

 the canal-system later on. This latter interpretation I am 

 in a position not only to thoroughly indorse, but to further 

 prove that these ciliated chambers are derived by a process 



* This sheath or lorica, in order to economize space, is represented in 

 its entirety in only one of the figures illustrative of this species. 



