60 BRYOZOA ECTOPROCTA. 



(pallial cavity, sucker). The internal organs, furthermore, are packed 

 into the smallest space possible. We sliall therefore not be surprised 

 at the absence of the coelom in the larva, although, from a com- 

 parison with the Adinotrocha, we should have expected it to be 

 present. The coelom, even in adult forms of marine Ectoprocta, is, 

 in a certain sense, degenerate (the peritoneal epithelium being 

 wanting); the cause of its excessive degeneration in the larva, 

 however, is to be sought in the conditions just mentioned. A similar 

 temporary obliteration of the interior of the larva is to be found, 

 for instance, in the Platmla-lnrva. of the Cnidaria. 



If we now consider the Phylactolaematous larva in the light of 

 what has been said above, we shall find that the central cavity Avithin 

 it, taking into account its further development, must be assumed to 

 be the coelom. In this respect, then, the embryo of the Phylactolae- 

 mata, as compared with that of the Gymnolaemata, recalls more 

 primitive conditions. We must not, however, forget that, in other 

 respects, this larva has undergone the most far-reaching degenera- 

 tions. The development of a large central cavity inside the ciliated 

 larva may be connected with its life in a specifically lighter medium 

 (fresh water). We find, for instance, that the larva of Spongilla is 

 distinguished from somewhat similar marine Sponge larvae by the 

 possession of a larger cavity. 



LITERATURE. 



Cyphonautes. 



Besides tlie works of Ehrenbbrg, Joh. Mullbr, Semper, Allman, 

 J. Barrois, and H. Prouho (Xo. 28 and 28b) cf. : 



1. Claparede, E. Beobachtungen iiber Anatomic und Entwick- 



lungsgeschichte wirbelloser Thiere an der Kuste der Normandie. 

 Leijtzig, 1863. 



2. Hatschek, B. Embryonalentwicklung und Knospung der 



Pedicellina echinata. Zeitschr. f. Wiss. Zool. Bd. xxix. 

 1877. p. 533, etc. 



3. OsTROUMOFF, A. Note sur la metamorphose du Cyphonautes. 



Zool. Am. Jg. viii. 1885. See also below, jS'o. 26. 



4. Eepiachoff, W. Bemerkungen iiljer Cyphonautes. Zool. Anz. 



Jg. ii. 1879. 



5. Schneider, A. Zur Entwicklungsgeschichte und systematischen 



Stellung der Bryozoen und Gephyreen. ArcMv. f. Micro. 

 Anat. Bd. v. 1869. 



