Hyatt. 64 [March 5, 



principal basis upon which Dr. Minot founded his comparisons 

 with the ovum, and having been quoted in his paper need not be 

 reiterated. 



There is, however, no " a priori " reason why the femino- 

 nucleus in the spermatocyst after becoming sexually useless should 

 not acquire secondary habits and be either lost, resorbed, or 

 divide and help in forming the tails of the spermatozoa. It 

 would be unfavorable to our position, if these tails were carried 

 into the ovum and were influential in fecundation. The body of 

 the spermatozoon, however, appears to be the part which pene- 

 trates the ovum in the forms so far known, and the tails are 

 apparently lost, or resorbed, or used to plug up the micropylar 

 opening. 



It is also not essential to Minot's hypothesis, that the nucleus 

 in the most primitive forms should be bisexual, but simply that 

 it should contain elements which are capable of being differen- 

 tiated into two parts and that these two parts may either have 

 had, or simply acquired during ox after separation the distinctive 

 qualities of the peripheral * male, and central female nuclei. 

 The elements as they exist in the primitive nucleus may have 

 been, for all that we know, homogeneous ; but it is plain from the 

 researches of authors that the primitive differentiation of the 

 nucleus into two parts ia the first well-marked appearence of 

 reproductive functions and differences in Protozoa. 



We see no difficulty in admitting Whitman's proposition (Em- 

 bryology of Clepsine), that fecundation is essentially the addition 

 of living active matter, " the fusion of the corresponding parts of 

 two separate individuals ; " but we should add, that this is merely 

 another expression for the character of all fecundative pro- 

 cesses, viz. : that they are all essentially due to the need of cross 

 fertilization. 2 That a part of the nucleus in one animal should 

 become specialized for the performance of this function and that 

 the similar part of the nucleus of another should be thrown 

 away in order to create a vacancy for it does not seem at all 

 contrary to the self evident truth of the fusion hypothesis, it 



1 These terms were first used by Van Beneden, La Maturation de 1' oeuf, Bruxelles, 



1875. 



2 We should also find it necessary to substitute the word " complementary " for 

 " corresponding" in Dr. Whitman's sentence quoted above. 



