igS CYTOLOGY 



CHAP. 



(1912) himself found that in sea-urchins the chondriosome apparatus 

 introduced by the spermatozoon undergoes no metamorphosis, but is 

 relegated unchanged to one of the first two blastomeres. An exactly 

 similar process has been described for various mammals by van der 

 Stricht (1910) in the bat, and by Lams (1913) in the guinea-pig (Fig. 82). 

 In order to save the theory of chondriosome inheritance, it was suggested 

 that the blastomere lacking the chondriosomes takes no part in the 

 formation of the adult, but that in the mammals (van der Stricht) the 

 trophoblast develops from it, and in Echinoderms (Meves) that part 

 of the pluteus larva which is cast off at metamorphosis. This conjecture 

 must be considered very improbable, for the pluteus is an organism 

 quite as specific as the adult sea-urchin and quite as much in need of 



p.bl jo.6.11 



n 



^r 



B 



Fig. 82. 



The chondriosomes in the fertihzation and cleavage of the guinea-pig's ovum. (After Lams," /I .i?., 1913.) 

 A, entry of the spermatozoon ; B, 2-celI stage, the tail (including the chondriosome apparatus) of the 

 spermatozoon lying unchanged in one blastomere. 



p.b. I., first polar body; p.b. II., second polar body ; I, tail of spermatozoon ; II., metaphase II. 



a complete hereditary outfit. It has, however, been rendered still more 

 improbable — if not indeed definitely disproved- — by Meves himself, 

 who later (1914) traced the chondriosome mass of the male gamete 

 in Parechinus up to the 32-ceU embryo. At this stage it is still compact 

 and unchanged, and is therefore of course only to be found in one cell. 

 All the other 31 cells therefore contain no part of the male chondriosome 

 apparatus, so that it is established that this is not essential to the develop- 

 ment of the Echinoderm. 



Whilst thus the behaviour of the male chondriosome mass in 

 fertilization is alone enough to destroy all claim to the idioplasmic 

 nature of chondriosomes, unless and until new knowledge of an unfore- 

 seen nature is forthcoming, there are several other almost equally con- 

 vincing items of evidence. It is not necessary to labour the point of the 

 colossal excess of the chondriosomes in the egg over those brought in 



