222 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the ova are not incubated in the maternal organism, although he allows that 

 this is by no means an essential character. The author does not agree with 

 Delia Valle in believing that there is any relationship between Distaplia 

 and Aplidium ; from a comparative study of the migratory buds and ova he 

 comes to the conclusion that the former genus finds its closest allies in 

 Anckinia and Boliolum ; Distaplia is to Anchinia what the Diplosomidse are 

 to the PyrosomatidsB — the fixed representatives of a pelagic form. 



The free buds are true diblastulae, comparable to the gemmiparous 

 stolon of PeropJwra, which also arises at exactly the same anatomical point 

 in each individual of the colony. 



p. Polyzoa. 



Metamorphosis of Bryozoa.* — M. J. Barrois thinks that in considering 

 the metamorphosis of the Bryozoa we ought to distinguish two great types, 

 one represented by Phoronis and one by PediceUina. The former is cha- 

 racterized by the predominance of the ventral surface, which forms the 

 whole of the body, and by the reduction of the dorsal surface to a terminal 

 region ; in the latter the aboral surface (or the cephalic end of the trocho- 

 sphere) predominates, and extends above the whole oral (somatic) surface 

 to form the whole of the integument of the adult, the somatic surface being 

 pushed into the interior. He does not look upon what obtains in the 

 Chilostomata as being really an intermediate condition ; while not denying 

 that the evagination of the internal sac of the larvae of the Ectoprocta may 

 be considered as the same thing as the evagination of the ventral tube of 

 Phoronis, he notes that it does not play a determining part in the acquisi- 

 tion of the characters of the adult, and that it is not followed, as in 

 Phoronis and Bhahdopleura, by the reduction of the whole of the aboral 

 surface ; this rather continues to form an umbrella. 



Both types of development are derived from the trochosphere, the 

 author withdrawing his previous comparison of Bryozoa to a rotifer fixed 

 by its oral surface ; that of most Bryozoa is due to the predominance of 

 the cephalic and the indrawal of the somatic region ; that of Phoronis (and 

 perhaps also Mhahdopleura) to the predominance of the ventral face and the 

 crowding of the whole of the dorsal surface (the preoral lobe and velum 

 being here included) into a restricted portion of the terminal region. The 

 Entoprocta are regarded as being the most primitive of the Bryozoa. 



The conclusions of this memoir are based on the study of a number of 

 difierent forms, amongst which are Lepralia pallasiana, Bugula flahellata, 

 Serialaria lendigera, which is the most typical example of the tun-shaped 

 larvfe, and PediceUina. The theory of alternation of generation is 

 altogether rejected. 



New Family of Bryozoa.t — Dr. J. Jullien institutes the new family of 

 Cosiulidse iov th.Q Crihrilina of Gray; Escharella arge D'Orbigny may be 

 regarded as the typical species ; the seventeen recent and fossil genera of 

 which it is composed are defined, and five new species (two new genera) 

 are described. 



Arthropoda. 



Spermatogenesis of Arthropods.l — Prof. G. Gilson has communicated 

 a lengthy memoir in which some of his results on the spermatogenesis of 

 Arthropods are set forth. After a careful review of the history and a dis- 



* Ann. Sci. Nat, i. (188G) 194 pp. (4 pis), 

 t Bull. Soc. Zool. Fiance, xi. (1886) pp. GOl-20 (4 pis.). 

 . { La Cellule, i. pp. 1-188 (8 pis.). See this Jourual, ante, p. 69. 



