536 SUMMARY OF CURRENT RESEARCHES RELATING TO 



From what has been paid it will be plain tbat Van Lint believes in 

 the origin of the unisexual state from a primitive hermaphrodite one, 

 traces of which persist ; that ho attaches great importance to the de- 

 pendence of the soma on the gonads, and to the dependence of the 

 sex-cells on the state of the soma ; aud that he does not believe in 

 the germ-plasm concept. 



The theory, which is a co-ordination of the five hypotheses above 

 summarised, may be made quite clear by taking a particular case. If a 

 relatively feeble ovum is fertilised by a relatively vigorous spermato- 

 zoon, tho rtsult will be a female offspring. "What are the steps that 

 lead to this remarkable conclusion ? The fertilised ovum in question 

 will have the spermatozoon's qualities dominant ; the embryo will 

 therefore have a masculine soma (of paraspeunatozoul cells) ; to balance 

 this dominant masculinity the gonad must be female. 



The author proceeds to explain what is meant by the relative vigour 

 of a cell, and the vital force of an organism (which involves a complete 

 medical examination under six heads), but he explains that the certain 

 sign of a man's being more vigorous than his wife is his having a 

 daughter. " Le sexe de l'enfant tranchera la question." 



It is next pointed out that " crossed inheritance " — the son taking 

 after his mother, the daughter after her father — is readily interpreted 

 by the theory expounded. The son is the result of a more vigorous 

 ovum fertilised by a less vigorous spermatozoon, the somatic cells must 

 balance the gonads, therefore they must be feminine, and therefore the 

 boy is his mother's image. 



In the eighth chapter the author seeks to show that the available 

 statistical and experimental results, many of which are summed up in 

 Tlie Evolution of Sex by Geddes and Thomson (4th edition, 1901), 

 are in harmony with his theory, or may be harmonised with it. He 

 concludes by showing that the so-called auto-regulation of the propor- 

 tions of the sexes is readily explicable on his theory, for it is the more 

 feeble which nature insists on replacing. 



External Phenomena of Fertilisation.* — A. H. E. Buller has par- 

 ticularly studied Echinoid ova and spermatozoa. His chief results are 

 the following. The meeting of the spermatozoa with the outer surface 

 of the gelatinous coat (zona pellucida) is a matter of chance, and not 

 due to chemotaxis. In passing through the gelatinous coat the 

 spermatozoa follow a more or less radial directiou, but this is not due 

 to any chemotactic substance being excreted from the egg ; it is possibly 

 due to stereotaxis, but a purely mechanical explanation seems to the 

 author more probable. The spermatozoa do not respond to tonotactic 

 or heliotactic stimuli, and are probably not chemotactically sensitive. 



On coming in contact with a surface bounding their medium, the 

 spermatozoa cling to it, and usually continue for a time to revolve upon 

 it in (from their point of view) a counter-clockwise direction. This 

 statement applies to all the groups of Echinoderma. The spermatozoa 

 easily become attached to glass and other surfaces by the tips of their 

 conical heads. This phenomenon doubtless plays a role in causing the 

 spermatozoa to bore through the gelatinous coat after having come in 



* Quart. Journ. Micr. Sci., xlvi. (1902) pp. 145-76 (4 figs.)- 





