PRESENT STATUS OF CHONDRIOSOME PROBLEM. 79 



Finally we come to the hypothesis according to which the 

 chondriosomes represent the idioplasm contained in the proto- 

 plasm of the seminal cells. We must find out first what becomes 

 of the male chondriosomes in the process of fertilization. Al- 

 though one of the first studies of this process, that made on 

 A scar is megalocephala by van Beneden, showed that the whole 

 spermatozoon may enter the egg, the great majority of biologists 

 have accepted the dogma of the monopoly of the nucleus as 

 carrier of the idioplasm. The reasons for that attitude are 

 obvious. First, in most cases, only the nucleus of the spermato- 

 zoon was detected in the egg; further, investigators were 

 quite naturally hypnotized by the beautiful karyokinetic figures 

 which they saw formed in the fertilized egg at the expense of the 

 pronuclei. Yet, after van Beneden, a number of other authors 

 (Kostanecki, Nekrassof, Lams, etc., in invertebrates; Fick, 

 Nicolas, Michaelis, Van der Stricht, etc., in vertebrates) have 

 demonstrated that other parts of the spermatozoon are also 

 carried into the egg. The hypothesis in which the chondrio- 

 somes represent an idioplasmic substance has given a renewed 

 interest to these observations which had been considered as 

 exceptional cases, and recent observations, made under the 

 impulse of the same hypothesis, are likely to lead us to a recon- 

 sideration of our conception of the morphology of fertilization. 

 I need only mention in this connection the case of the sea-urchin. 

 It was generally accepted that only the nucleus and the so-called 

 "middle-piece" penetrate into the egg and that the tail is left 

 without. Recent observations, however, made with special 

 care and a more refined technique, have shown that the tail also 

 enters. Let us not forget, however, that the crucial point to 

 determine is not whether the tail, but whether the chondriosomes 

 are carried into the egg. As I pointed out when speaking of the 

 structure of the spermatozoon, these questions have no connec- 

 tion. One can readily conceive of a type of spermatozoon in 

 which only the head would penetrate, and yet the chondriosomes 

 would enter the egg at the same time. Such a type exists, as a 

 matter of fact, in a number of invertebrates, for instance the 

 ascidians Phallusia and Ciona. 1 



1 In these two species, however, the tail also is found in the egg. 



