'PHYSIOLOGICAL UNITS* 87 



through the process of segmentation, but even reached the stage 

 of the quaint easel-like Pluteus larva.' 



In both these latter sets of experiments it is to be presumed that 

 the eggs had undergone the usual reducing division and that the 

 number of chromosomes had been reduced to half their usual 

 number : it is extremely interesting to find, therefore, that physical 

 or certain common chemical stimuli were in these cases capable 

 of replacing the stimulation usually induced by (the chemical and 

 molecular) changes emanating from spermatozoa. Then, again, 

 there can be no doubt that in the 'merogonie' experiments in 

 which de-nucleated eggs of the sea-urchin were fertilised by the 

 spermatozoon of another sub-species, we have a related though 

 opposite form of ' unisexual ' development taking place, notwith- 

 standing the presence of only one half (in the spermatozoan 

 nucleus) of the ordinary number of chromosomes belonging to the 

 species. This latter case is, however, far more remarkable than 

 the other variety of 'unisexual' development, because of the 

 minute size of the spermatozoon as compared with that of the 

 ovum. 



Facts very similar to those we have just been recording are 

 known to occur also in the vegetable kingdom, and especially 

 among ferns, as was brought out by a skilled writer in " The Times " 

 (January, 1904) when calling attention to a remarkable discovery 

 laid before the Royal Society by Prof. Farmer, in conjunction with 

 Messrs. Moore and Walker, in regard to the chromosomes in many 

 of the cells of cancerous growths. From this article I venture to 

 make the following interesting quotation concerning these new 

 investigations : — 



" They have grown out of a close study of the reproductive 

 processes in animals and plants, and furnish an example of the 

 practical results which frequently follow from what we are too 

 often apt to disregard as the pursuit of pure science." 



"Your readers may be familiar with the fact that a fern forms 

 spores, these same spores when ripe fall upon the ground, and 

 there grow into little heart-shaped plants which are not in the 

 least like ferns, and are called by botanists prothallia. It is upon 



' According to Weldon (" The Lancet," February 4th) Loeb has since succeeded 

 in bringing about similar results " by the presence of a large quantity of carbon 

 dioxide in the sea water " — experiments which have been confirmed by Delage. 

 The latter investigator has quite recently recorded other remarkable results 

 (" Compt. Rend.," May 22, 1905, p. 1369) with a solution of chloride of manganese 

 in distilled water, and also with a solution of monobasic phosphate of soda. 



