184 Mr. W. H. Benson on new species of Cyclostoma. 



the first steps in the formation of an embryo." These con- 

 siderations become analogically of importance in leading ns to 

 the discovery of the real history of the Olacacea. Something 

 in relation to this subject might be learned, if we could better 

 understand the origin and development cf the embryo under 

 ordinary circumstances, for the facts are still undetermined that 

 can prove which of the two theories of the nature of vegetable 

 reproduction is founded on truth ; the one maintaining that the 

 pollen-grain penetrates the embryo-sac, and hence comes into 

 immediate contact with the body of the nucleary vesicle, in order 

 to effect its fertilization ; the other denying this assertion, and 

 declaring that it does not penetrate the sac, but merely discharges 

 its function of impregnation, by external impression. Similar 

 theories have long been disputed among zoologists, some con- 

 tending that the spermatozoon does not penetrate the ovum in 

 order to effect its impregnation, as mere external impact is suf- 

 ficient to accomplish this function, while others declare the 

 necessity of immediate contact, and that in proof of this they 

 have seen the spermatozoa within the shell of the ovum. This 

 point has just been determined by Mr. Newport, in a very in- 

 teresting paper read before the Linnsean Society, in which he 

 proves satisfactorily that the former view is conformable to 

 truth. He has ascertained the important facts, that the presence 

 of active spermatozoa are absolutely necessary to impregnate the 

 ovum ; that this is effected by simple impact ; he has noted the 

 time necessary to complete the operation, and has observed the 

 internal change that immediately takes place in the body of the 

 nucleus ; and moreover he has found that the spermatozoa, after 

 producing this effect by simple external impact, become inert 

 and lose all power of motion. Mr. Newport has suggested that 

 these circumstances, by analogy, may assist in determining the 

 theories in dispute among vegetable physiologists ; and he has 

 pointed to the curious fact recorded by Mr. Griffith (Linn. Trans, 

 vol. xx. p. 393) of the irritability or oscillatory motion seen within 

 the boyaux of the pollen-grains of Dischidia at the period of 

 impregnation of the ovules, which may perhaps be in some degree 

 analogous to the vivacity of spermatozoa under parallel circum- 

 stances. 



XVI. — Geographical Notices, and Characters of fourteen neiv spe- 

 cies of Cyclostoma, from the East Indies. By W. H. Benson, 



The following new species of an interesting genus of operculated 

 Land-snails belong chiefly to the mainland of India, and were 

 collected in the Sikkim Himalaya; among the hills to the north- 

 east of Bengal, and in the Peninsula of Southern India, from the 



