No. 542] CHROMOSOMES IX EC III SOW LARVAE 



75 



dividuals will be females, the reverse of our heliei' con 

 cerning the naturally parthenogenetic egg of the I mm-. In 

 cases similar to those described by Iialtzer for lulihtus, 

 half the adults will be males and half females. 



A prediction as to other characters is difficult to make, 

 for the fact that one species is dominant over another 

 with reference to larval skeletal characters give no idea 

 as to other characters. 



Nevertheless, in the cases of partial arrhenokaryosis 

 which I have mentioned we should expect a region of the 

 larval body containing only paternal nuclear material to 

 place its stamp on that part of the adult body arising 

 from it. A natural hybrid showing pure regional resem- 

 blances to one species or another is theoretically possible 

 and would find its explanation in partial arrhenokaryosis. 



For the inheritance of most characters we must fall 

 back on our knowledge of natural echinoderm hybrids, 

 which is increasing steadily. 



We should expect that where parts of both contribu- 

 tions of chromatin have been retained and an inter- 

 mediate pluteus has resulted the adult will be of the 

 mixed type. One of the supposed Echinoid hybrids de- 

 scribed by Mortensen fulfils this expectation. 



The proof of these predictions lies in the rearing of 

 hybrid larva? to the adult condition. This we know to be 

 possible. It requires only laboratory advantages of an 



