ZOOLOGY. 345 



Times, 



Ascaris mcgalocephala IG 



Strongylus armatus 86 



" tetraccuithns (in 07 out of 80 horses) 78 



Oxyuris curvula 3 



A NEW TYPE OF PARASITIC WORMS. 



Surgeon-Major G. E. Dobson has recently made known a reraarlcable 

 parasitic worm found in the intestine of an African bat {Megaderma 

 from). This has hitely been examined by Dr. J. D. McDonald* as well 

 as by Surgeon l^obson. The former remarks that at first he agreed 

 with Surgeon Dobson in thinking that it represented a new order of 

 Annelids, but he is now disposed to look upon it as a new type, whose 

 alliance is rather with the Xematoda. Surgeon Dobson considers it as 

 the type of a new order of worms, which he calls Metabdellada, and 

 which he refers to the "Archieostomata," among which, it is to be inter- 

 posed between the Itotifers and the Trematods. 



THE CLASS OF ORTHONECTIDS.t 



In 1877 Mr. A. Giard, of Paris, described some parasitic a .imals of 

 very low organization as the constituents of a peculiar class to which he 

 gave the name Orthonectida. These Orthonectida i) resent, as a perma- 

 nent feature of their existence, the plauula-form, which is one of the em- 

 bryological stages of most animals. They occur as parasites in Nemer- 

 teans and Ophiuroids. Mr. Giard has since suiiplemented his original 

 observations and studied their reproduction. Their movements, inde- 

 pendent of vibratile cilia, are due to the presence of muscle-like bands 

 belonging to the endodermic cells and forming a splanchno-pleural 

 "pseudo-mesoderm." lieproduction is effected in two ways: (1) sex- 

 ually and (2) by gemmiparity. In the former course it is (a) by the for- 

 mation of a blastula or (h) by the jiroduction of an epibolic ga,strula wMch 

 finally closes, and, in both cases, there ensues a permanent planula state 

 with a metamerized ectoderm. In the latter course gemmiparity super- 

 venes in the interior of enormous sporocysts formed by the endoderm of 

 the progenitve animal. It is as a result of gemmiparity that the Ortho- 

 nectids are met with in abundance in their host. The Orthonectids, it is 

 concluded, "are Gastrseada brought by parasitism to the state of planula^''^ 

 and their importance on the "Gastra3a theorj^" is very great. (See, 

 also, Metschnikoff" in Zool. Anzeigcrj vol. ii, j). 547.) 



*Macdoiiald (.Jolin Deuis). Ou tlie anatomy of a new parasitic worm found in the in- 

 testine of a bat (Megaderma frous). Ann. Mag. Nat. Hist., (5,) vol. vi, pp. 409-411, 

 pi. 21. Also, Dobson (G. E.). Note on Pterogodermatiten Macdoualdii ; the type of a 

 new order of Vermes. Ann. Mag. Nat. Hist. (.5), vol. vi, pji. 412-414. 



t Giard (A.). On the organization and classification of the Orthonectids. Ann. and 

 Mag. Nat. Hist., (X>,) vol. iv, pp. 471-473. From Comptes liendus, September 22, 1879. 



