4 The Ohio Journal of Science [Vol. XVII, No. 1, 



The earliest cases of matrocline hybrids appear to be those 

 between different orders or genera of echinoderms. These were 

 not always reciprocal crosses. Such crosses have been made 

 possible largely by the work of Loeb and others on the induction 

 of artificial parthenogenesis, through chemical changes in the 

 sea water. Loeb himself fertilized sea-urchin eggs with the 

 sperm of starfishes and ophiurans. The larv^ were purely of the 

 maternal (sea-urchin) type. Godlewski fertilized sea-urchin 

 •eggs with crinoid sperm. The larvae were again purely maternal. 

 The most obvious explanation in each case is that the type of 

 larval development is determined by the cytoplasm of the egg. 

 Too much stress is not to be laid upon this evidence, however, 

 for recent work of Baltzer has shown that there may be irreg- 

 ularity of the behavior of the chromosomes in the two recip- 

 rocal hybrids; so that these matrocline hybrids may some day 

 become most excellent evidence of the importance of chromo- 

 somes in heredity. This objection can hardly be urged against 

 other experiments of Godlewski, in which fragments of sea- 

 urchin eggs that contained no nuclei were fertilized with crinoid 

 sperm. Even if irregularities in the behavior of the chromo- 

 somes occurred, and some of the chromosomes were lost, what- 

 ever chromosomes remained must have been paternal. Yet 

 larvae from these egg fragments were purely maternal in type. 

 This result is not the universal one, it is true, for Boveri obtained 

 precisely the reverse effect in another cross. But for those 

 ■cases in which the larva produced by merogony (that is, the 

 fertilization of egg fragments) is maternal, there seems little 

 room for any other conclusion than that the cytoplasm of the 

 egg is responsible. 



Not all matrocline hybrids, be it pointed out in leaving this 

 type of evidence, are evidence of cytoplasmic influence. There 

 .are matrocline hybrids in the evening primrose, Oenothera. 

 But there are also patrocline hybrids in the same genus, that is, 

 reciprocal hybrids that resemble the father more than the 

 mother. Oenothera is probably not a lawless being, but so far 

 its laws have baffled all its students. When patrocline hybrids 

 are finally explained in Oenothera, the explanation may well 

 be such as will also explain matrocline hybrids without an 

 appeal to the cytoplasm. But this anticipated defection of the 

 evening primrose from the ranks of matrocline hybrids which 

 owe their maternal resemblance to the cytoplasm of the egg, 



