220 SUMMAEY OF CURRENT RESEARCHES RELATING TO 



gradual increase in calibre of the tubules forming tbe primitive network 

 and have become isolated into metamerically disposed tufts of tubules, 

 corresponding more or less to the setge ; these separate nephridia have 

 become ultimately reduced to a pair in each segment. 



"New Earthworm.* — Mr. H. Garman describes a new American earth- 

 worm under the name of Diplocardta communis. It belongs to the family 

 of the Acanthodrilidse, but is distinguished by the absence of a subneural 

 vessel, and the existence of a double dorsal vessel, the two halves of 

 which are separate throughout their length, except where they pass 

 through the septa between the somites. Sixteen species of American 

 earthworms have been named, and there is an undetermined species of 

 PericJiseta, 



New Genus of Eudrilidse.t — Dr. D. Eosa describes a new genus of 

 the family Eudrilidee — Teleudrilus ragazzii, from Africa (Scioa), which 

 he regards as throwing some light on tbe characters of Eudrilus. The 

 new genus is certainly very nearly allied to it, and from its examination 

 the author concludes that it is probable that some of the more divergent 

 characters ascribed to Eudrilus cannot be really sustained. It is certain 

 that all these aberrant characters are not demonstrable in Teleudrilus. 

 He discusses the aberrant features noted by Beddard, and would not 

 separate either Eudrilus or Teleudrilus from the other members of the 

 family, for which he gives a somewhat modified diagnosis. He also 

 describes a new species of Acanthodrilus {A. scioanus). 



Indian Perichsetidse.l — Dr. D. Eosa describes certain Indian Peri- 

 chgetidsB found by Sig. L. Fea, viz. Perionyx excavatus Perr. from 

 Irawaddy and Tenasserim ; Megascolex armatus Bedd. from Mandalay ; 

 Perichseta fese sp. n., from Tenasserim ; and Perichseta hirmanica sp. n., 

 from Irawaddy. He divides the Perichsetidse into two sets : (a) with 

 the orifices of the male ducts and of the spermathecas contiguous — 

 gen. Perionyx; (&) with the orifices of the male ducts and of the 

 spermathecse distant — gen. Megascolex and Perichseta. The last two 

 genera are thus distinguished : in the former the setse are in interrupted 

 rings, and there are no intestinal cseca ; in the latter the setae are in 

 continuous rings, and intestinal caeca are present. The characters of all 

 the four species are given at length. 



j3. Nemathelminthes. 



Fertilization and Segmentation in Ascaris megaloeephala.§ — Dr. 

 Th. Boveri, continuing his " Cell-Studies," describes in great detail the 

 phenomena of fertilization and segmentation in the ovum of Ascaris 

 megalocephala. On this subject at least eight important investigations 

 have been made since Schneider's memoir in 1883, and, in spite of mani- 

 fold contradictions, it would be vain to assert that there has not been 

 great progress towards certainty and clearness. To this end the present 

 memoir contributes much. Dr. Boveri discusses the various stages and 

 aspects in eight chapters, extending over nearly 200 pages, and illus- 

 trates them in five most beautifully executed plates which well deserve 

 to be ranked among the masterpieces of microscopic draughtsmanship. 



* Amer. Natural., xix. (1888) pp. 1030-1. 



t Ann. Mus. Nat. Geneva, vi. (1888) pp. 571-92 (1 pi.). 



J Ibid., pp. 155-66 (1 pi.). 



§ Jenaische Zeitscbr. f. Naturwiss., xxii. (1888) pp. 685-882 (5 pis.). 



