144 J. DUESBERG 



Again as in many and perhaps all cases, the last stages of 

 spermiogenesis bring about a change in the behavior of the chon- 

 driosomes towards reagents. It is well known that, in the mam- 

 malian testicle for example, the chondriosomes become more and 

 more resistant to acetic acid as spermiogenesis progresses.^ The 

 test of this resistance was not made here, but it was found that 

 the chondriosomes of the last stages are structures much less 

 labile than the chondriosomes of the early stages and are conse- 

 quently much easier to bring into evidence. 

 « 



The preceding description of the spermatozoon of Fundulus 

 agrees in the main with Retzius' observations on the spermato- 

 zoon of other teleosts, though differing in the details. It helps 

 at the same time to emphasize the similarity in structure between 

 these spermatozoa and those of a large number of invertebrates, 

 while the spermatozoa of selachians and of the higher verte- 

 brates are widely different. 



From the same description it also appears very probable that 

 the male chondriosomes, owing to their close contact with the 

 nucleus, are carried into the egg at the time of fertilization. 

 Though this can be ascertained only by the study of the fertiliz- 

 ing process, the evidence accumulated by an imposing number 

 of observations made upon almost all classes of animals, especi- 

 ally in recent years, is certainly very much in favor of the theory 

 according to which the penetration of the male chondriosomes 

 into the egg is a general phenomenon. Shaffer who mentions 

 only Meves' observations on Ascaris and Vander Stricht's on 

 the bat, overlooks the largest part of this evidence. That Lillie 

 ('12) found in Nereis that the 'middle-piece' and the tail of the 

 spermatozoon do not enter the egg does not prove that the chon- 

 driosomes are not carried into it. 



I still believe, as in 1915, that the real objection to the admis- 

 sion that the male chondriosomes play a role in heredity is to 

 be found in Meves' observations on the echinoderm-embryo ; 

 why their admitted chemical composition should plead against 



^ I found recentl}^ that the same changes take place in the spermatids of 

 opossum. 



