Heredity in Fiindulus Hybrids 159 



increased variability frequently manifests itself from the first and 

 must be considered as one of the early effects of the foreign sperm. 



Can the data derived from remote heterogenic crosses, such as those 

 described by Loeb and Godlewski be safely used as criteria for positing 

 a theory of normal biparental inheritance ? 



An examination of the work of the two experimenters mentioned 

 and of several other contributions of more recent date, reveals the 

 fact that the spermatozoon in no case functions completely or 

 normally. 



In fact, as Loeb himself has suggested, it seems highly prob- 

 able in crosses between different orders, such as echinoids and 

 crinoids, that the spermatozoon performs only one of its functions, 

 that of initiating development, and that the process of develop- 

 ment is thenceforth parthenogenetic. 



In Godlewski's experiments it can scarcely be doubted that the 

 sperm nucleus enters the egg and fuses with the egg nucleus. 

 The figures show, however, that the chromatin material remains 

 inactive and that the male pronucleus, instead of increasing in 

 size until it equals that of the female pronucleus, remains in its 

 concentrated condition until it fuses with the latter. This fusion 

 has every appearance of a mechanical absorption of a foreign 

 particle. In no place does Godlewski indicate that the chromatin 

 of the sperm nucleus takes part in the mitoticdivisionsof cleavage. 

 It operates only to the extent of slightly hindering the rate of 

 early cleavage and probably is soon entirely absorbed by the egg 

 protoplasm. 



A still clearer case is that described by Kupelwieser,^ who fer- 

 tilized the eggs of an echinoid with the sperm of a mollusc. In this 

 case both description and figures show clearly that the sperm 

 nucleus never breaks up into chromosomes, but remains inactive 

 in the form of a mere lump of inert substance, apparently com- 

 pletely incompatible with the materials of the egg nucleus. In 

 this form it is carried along through several cleavages and is sub- 

 sequently absorbed. It should not be surprising then to find 

 such hybrids, if hybrids they may be called, showing pure maternal 



-Arch. f. Entw. Mech., vol. 27, pp. 434-462. 



