204 SUMMARY OF CURRENT RESEARCHES RELATING TO 



i 



South American Geoscolecidae.* — Dr. W. Miohaelsen gives a short 

 description of Fimoscolex ohausi g. et sp. n., which is nearly related to 

 Geoscolex F. S. Leuckart (with which Tyhonus Mchlsn. should be united). 

 It has, however, a single ventro-median male aperture (two in Geoscolex), 

 a single pair of calciferous glands restricted to the 12th segment (ex- 

 tending into the 11th in Geoscolex), and no special blood-vessels to the 

 calciferous glands (present in Geoscolex). The author also describes 

 Anteus columbianus sp. n. 



Encystment of Pachydrilus catanensis Drago.t — Dr. Umberto 

 Drago replies to Cognetti's J criticisms of his statements on this subject. 

 Cognetti suggested that what Drago regarded as probable encystment 

 was merely the ordinary process of cocoon formation. Drago replies 

 that in composition the " cyst " resembles more closely the cysts of 

 certain parasitic worms than the cocoon of an Oligochsete, and that, 

 as the species is adapted to a commensal and almost to a parasitic life, 

 there is nothing intrinsically improbable in the suggestion that en- 

 cystation occurs. The fact that the " cyst " included two individuals is 

 further not an argument against this view of its origin ; for the cysts of 

 certain worms (Trichinella spiralis, Gysticercus megabothrius, Ascalabotes 

 mauritanicus) may contain from two to seven individuals. On the whole 

 therefore Drago is of opinion that his hypothesis is the one which best 

 fits the facts. 



Genus Perichseta and Zoological Nomenclature. § — Dr. E. Horst 

 publishes a brief note protesting against Michaelson's recent proposal || to 

 substitute Amyntas for Perichseta, because the latter name had been used 

 by Eondani for a genus of Diptera, before being applied by Schmarda 

 to an earthworm. Horst reviews the somewhat chequered history of 

 Perichseta as an Oligochtete genus-name, points out the confusion which 

 must necessarily follow if it is now discarded, and notes that as Kon- 

 daui's Dipteran g6nus was merely a synonym for Phorocera Macquart, 

 the fact that he used the term does not vitiate Schmarda's use of it. 



Non-sexual Reproduction in Dero.H — Mr. T. W. Galloway has 

 been able to make observations on this subject in D. vaga (Aulophorus 

 vagus Leidy). He finds that in the non-dividing animal there is an 

 undifferentiated zone immediately in front of the anal segment, which 

 continually gives rise to new segments anteriorly. When budding begins, 

 a bud-zone is formed in one of these new segments, so that budding 

 must be looked upon as a specialised form of segmentation. There does 

 not seem to be any constancy as to the segment in which bud-formation 

 occurs. Division always occurs midway between two dissepiments. 

 Generally speaking the histology of bud-formation is the same as in 

 Ghsetogaster according to von Bock, but there are certain minor differ- 

 ences. Thus in Dero newly formed ciliated endoderm unites old endo- 

 derm and body- wall in the anal segment, while in Ghsetogaster the old 

 endoderm and the body-wall unite directly. There are also slight 

 differences in the formation of mouth and pharynx and of the nervous 

 system. 



* Zool. Anzeig., xxiii. (1900) pp. 53-6. f Tom. cit., pp. 18-21. 



% Of. this Journal, 1899, p. f)99. § Zool. Auzeig., xxiii. (1900) pp. 6-S. 



|| Beiliett Jahrb. Hamburg, wiss. Anstalt, xvi. (1899). 



«|f Bull. Mus. Comp. Zool. Harvard, xxxv. (1899) pp. 115-40 (5 pis.). 



