FERTILISATION 221 



Parthenogenetic development of starfish eggs has been produced 

 also by mechanical agitation ; ^ but it is possible, as Loeb ob- 

 serves, that the diffusion of carbonic dioxide, or some other gas, 

 into or from the eggs may be the real exciting cause. ^ 



Loeb found also that the unfertiKsed eggs of the Annehd, 

 Chwtopterus, could be made to develop into swimming larvae 

 by adding a small quantity of a soluble potassium salt to the 

 sea-water in which they were placed.* The same result could 

 be brought about by the addition of hydrochloric acid. The 

 eggs appeared to undergo development, as far as the trochophore 

 stage, but without segmenting. 



Lillie,* however, found that the nuclear divisions were 

 abnormal, and that the apparent trochophore larvae were 

 not typical, being in reahty merely " ciliated structures " 

 which were far behind the real larvae in organisation. But 

 BuUot ^ showed that in another Annehd, Ophelia, ova fertilised 

 by hypertonic sea- water underwent a regular segmentation. 



Loeb has shown that the ova of hmpets (Acmoea and Lottia) 

 could be artificially fertiUsed by the combined action of fatty 

 acid and hypertonic sea-water. This method also had the 

 effect of hastening maturation, since ova which could not be 

 fertihsed by spermatozoa could be made to develop into larvae 

 by the artificial treatment. It was found, further, that matura- 

 tion could be induced by the action of alkaline sea-water, and 

 that ova which were treated in this way could be fertihsed by 

 spermatozoa or artificially fertihsed.® 



Bataillon ' states that the unfertilised eggs of the lamprey, 

 and also those of the frog, can be made to undergo segmentation 



' Mathews, "Artificial Parthenogenesis produced by Mechanical Agitation," 

 Amer. Jour, of Phys., vol. vi., 1901. 



2 Loeb, The Dynamics of Living Matter, New York, 1906. 



' Loeb, "Experiments on Artificial Parthenogenesis in Annelids," &c. 

 Amtr. Jour, of Phys., vol. iv., 1901. 



* Lillie, " Differentiation without Cleavage in the Egg of the Annelid, 

 Ghcetopterus pergamentaceus," Arch. f. Entwick.-Mechanih, vol. xiv., 1902. 



^ Bullot, " Artificial Parthenogenesis and Regular Segmentation in an 

 Annelid (Ophelia)," Arch. f. Entwiok.-Mcchanik, vol. xviii., 1904. 



6 Loeb, Univ. of California Publications : Physiology, Berkeley, vol. i., 

 1903, and vol. iii., 1905. 



' Bataillon, " Nouveaux Essais de Parthenogen^se exp6rimentale ohez les 

 Vertfebr^s inf^rieurs (Bana fusca et Petromyzon planeri "), Arch. f. Entwick.- 

 Mechanik, vol. xviii., 1904. 



