ARTIFICIAL PARTHENOGENESIS AND HKKKDITY i".7 



the closure of the blastopore." I have been able to raise the 

 hybrid between Fundulus heteroclitus ? and Menidia, Clcnn- 

 labrus, and Stenotomus $ in large numbers beyond this stage. 

 These hybrids lived a month or longer, formed hearts, blood 

 vessels, eyes, and fins, but never hatched. With a few excep- 

 tions no circulation was ever established although the heart 

 beat for weeks. 



FIG. 87. Hybrid between Fundulus heteroclitus 2 and Menidia $, twenty 

 days old, showing purely maternal characters. 



Fig. 87 shows a three-weeks-old hybrid of Fundulus hetero- 

 clitus ? and Menidia $. The pure breed of Fundulus hetero- 

 clitus, of the same age, were already hatching. The hybrid 

 embryos had formed the pigment characteristic for the pure 

 breed of Fundulus heteroclitus. But the anomalies of the em- 

 bryo are very obvious. The embryo is rather small, owing to 

 the slowness with which these hybrids digest the yolk. Its 

 eyes are abnormal and approach the cyclopean condition. In 

 many specimens only irregular masses of pigment indicate 

 where the eyes should be. The head is comparatively small 

 and not bent as is characteristic for the pure breed. The heart 

 is developed but corresponds to an early stage in the develop- 

 ment. It beats regularly and at an almost normal rate. The 



