ZOOLOGY. 345 



Times, 



Ascaris megaloeephala 16 



Strongylus armatus ^Q 



" tetracantlius (in 67 out of 86 horses) 78 



Oxyuris curvula 3 



A NEW TYPE OF PARASITIC WORMS. 



Sui^eon-Major G. E. Dobsoii lias recently made known a remarkable 

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

 frons). This has lately been examined by Dr. J. D. McDonald* as well 

 as by Surgeon Dobson. 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 Nematoda. 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 Rotifers and the Trematods. 



THE CLASS OF OETHONECTIDS.f 



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

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

 gave the name Orthonectida. These Orthonectida present, as a perma- 

 nent feature of their existence, the planula-forin, which is one of the em- 

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

 teans and Ophiuroids. Mr. Giard has since supplemented 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." Reproduction 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 (b) by the production of an epiholic gastrula which 

 finally closes, and, in both cases, there ensues a i)ermanent planula state 

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

 veues 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 Gastraeada brought by parasitism to the state of planula,^^ 

 and their importance on the "Gastraea theory" is very great. (See, 

 also, MetschuikolF in Zool. Anzeigcr, vol. ii, p. 547.) 



*Macdonal(l (John Deuis). Ou the anatomy of a new parasitic worm found in the in- 

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

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

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



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

 Mag. Nat. Hist., (13,) vol. iv, pp. 471-473. From Comptes Eendus, September 22, 1879. 



