414 Mr. P. H. Gosse on the British Actinise. 



a worm closely allied to Gordius, found, in every instance, that 

 after twenty-four hours the larvre became more or less infected 

 with these embryos, which had penetrated into their bodies; 

 while the larvi3e of Yponomeuta being transparent, enabled this 

 sagacious observer to ascertain, by aid of the microscope, that 

 they did not contain any of these embryos before the experi- 

 ment of bringing the two into contact with each other was 

 performed*. Lespes also, while studying the Termites, found 

 whole nests destroyed by the embryos of a Nematoid worm just 

 like our microscopic Filarice, penetrating their bodies and be- 

 coming developed in the peritoneal cavity f, as in the instance 

 above mentioned in Nais. If, after this, the origin and mode of 

 introduction of Dracunculus into the human body be doubted, I 

 can only reply, that I shall be happy to see a better explana- 

 tion of it. The facts above stated appear to me as conclusive as 

 those of Cysticercus producing Tania, or tape-worm ; and there- 

 fore it remains only to determine which of the microscopic 

 Filaria produces Dracunculus in Bombay, — a point which the 

 marked forms of these worms respectively might be expected to 

 render not difficult of demonstration. Indeed, it so happens 

 that the so-called "Tank-worm" {Lfrolabesl palustris, mihi), 

 which I have taken from the "bathing-pool" of the school men- 

 tioned, as well as from other pools, tanks, and collections of 

 dirty fresh water in the island generally, comes nearest to Dra' 

 cunculus. The largest specimens are l-6th of an inch long, bi- 

 labiate, with an exsertile, sharp-pointed oesophagus ; the hepatic 

 sheath ending some distance from the termination of the intes- 

 tine ; the vulva opens in the female a little in front of the 

 middle of the body, and the anus posteriorly, just before the 

 body terminates suddenly in a whip-like tail. The penis in the 

 male is exsertile from the anus, very nearly close to the posterior 

 extremity of the body, which is so obtuse as to be almost trun- 

 cated. The tail of the young is semi-geniculated at the base, and 

 there is a gland close to the anus, as in the young Dracunculus ; 

 that of the adult female varies in length, and becomes curved 

 upon itself when short. 



XL. — Synopsis of the Families, Genera, and Species of the British 

 Actinia. By P. H. Gosse, F.R.S. 



In hac Synopsi includuntur tot species Zoophytorum Astrsea- 

 ceorum Britannicorum quot mihi adhuc cognitae sunt. Desunt 



* Ann. (les Sc. Nat. ser. 4. Zool. t. iv. p. 56, 1855. 

 t Annals, vol. xix. p. 388, 1857. 



J " A holder-on by the tail," which is a character common to all these 

 microscopic Filari<B. 



