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A smaller proportion of the embryos failed to emerge from the membranes. 

 These were helped out but showed the coiled tail so common among fish 

 embryos that seem to have thrived poorly. The hybrids, however, appeared 

 less healthy than a lot of normals that were fertilized at the same time, 

 and kept under the same conditions. These mostly lived three and four 

 days longer. As far as can be judged from this single experiment, it is 

 doubtful whether many of these hybrids, even with the care and proper con- 

 ditions supplied, could be successfully reared. 



Apeltes quadraciis, female, 



X 



Gasterosteus Mspiiiosus, male. 



Two tests were made. In one of them 18 per cent, of the eggs were 

 impregnated. The embryos showed the usual slowing in the rate of de- 

 velopment after close of cleavage. The development went to the stage of 

 hatching, two emerging but showing little vigor. They died after the sec- 

 ond day of emergence. The embryos that failed to emerge, for the most 

 part lived as long as the two which had hatched. The success of this cross 

 is probably the same as that of the reciprocal. 



Gasterosteus bispmosMS, female, 



Menidia notata, male. 

 The eggs of this stickleback are practically all impregnated when placed 

 with Menidia sperm. In the two experiments tried, 100 per cent, and 70 

 per cent, were fertilized. A small per cent, of these are polyspermic. The 

 development keeps well apace with the normals until toward the closure 

 of the blastopore. The embryo is laid down, the eyes are formed, but the 

 anterior region of body is quite heavy. Pigment forms and the heart is de- 

 veloped. I have never seen fins form in these hybrids. The embryos soon 

 die, owing possibly to the fact that the eggs even normally do not do well 

 in a fingerbowl of water. 



Menidia notata, female, 



X 

 Gasterosteus Mspinosus, male. 



This cross was made but once. All of the eggs were fertilized. The 

 development was followed to the closure of the blastopore. They doubtless 



