8O J. DUESBERG. 



We have observations, consequently, showing that the tail 

 of the spermatozoon, or part of it, penetrates into the egg. We 

 come now to the cases where the chondriosomes have actually 

 been found in the egg. Most of these cases have been described 

 recently under the impulse of the chondriosomal theory, and, 

 considering the short time intervening since the publication of 

 that theory, their number is already quite impressive. The 

 actual penetration of chondriosomes into the egg was seen long 

 ago, however, by L. and R. Zoja in Ascaris, and later by Vander 

 Stricht in the bat. To these observations have been added, 

 during the last seven years, a number of others: on the sea- 

 urchin, Phallusia, Mytilus and Filaria (Meves) and on Ciona 

 (Duesberg). Thus we already have observations on a number 

 of invertebrates (worms, ascidians, echinoderms and molluscs) 

 and vertebrates (mammals and amphibians for there is no doubt 

 from the observations of Pick and Michaelis that in Triton and 

 Axolotl also the male chondriosomes are carried into the egg). 



While things would thus appear to be in perfect agreement 

 with the theory according to which the chondriosomes are idio- 

 plasm, a difficulty, and a very serious one indeed, has arisen. 

 First, Vander Stricht and his pupils found in mammals that the 

 chondriosomal part of the spermatozoon (in the bat, the spiral 

 filament) passes unchanged into one of the first two blastomeres. 

 Similarly in the sea-urchin, the chondriosomal middle-piece is 

 found in one of the daughter-cells after the first division (Meves). 

 So far the difficulty could be met, for there is some reason to 

 believe that the two first blastomeres of the mammalian egg are 

 not equivalent, one of them possibly forming the trophoblast 

 only, the other the embryo, and a similar hypothesis could be 

 formulated concerning the sea-urchin, since the adult is formed 

 of parts only of the original embryo. Meves supposed that the 

 male chondriosomal substance would go over into these cells 

 which build up the definite animal. His further investigations 

 on the fate of the middle-piece, up to 32 blastomeres, show that 

 its fate is variable and that certainly not all cells of the young 

 sea-urchin will receive male chondriosomal substance. 



Here lies the real difficulty, and its weight seems overwhelming. 

 I would however warn against too hasty conclusions. A number 



