114 



eggs filled the pocket heaped full. The exposed surface of the eggs was 

 then closely spun over so that they were completely enclosed in a slightly 

 compressed spherical cocoon, suspended in the center of the sheet. The 

 edges of the sheet were then cut loose from the ground, carefully rolled up 

 with the mandibles and palpi and tucked up against the cocoon, being spun 

 fast as the work proceeded. This appeared as a rather prominent equa- 

 torial band around the cocoon at the line of attachment of the sheet. 

 The whole cocoon Avas strengthened by further spinning, and, when 

 finished, was fastened to the spinners and carried away. The whole was 

 completed in a little more than one-half hour. 



I have examined the cocoons of over fifty different species of Lycosidae 

 and all show their equatorial band more or less prominently, so that it 

 would seem that all the species adopt in general this same plan of con- 

 structing their egg-sac. 



Experiments in the Hybridization of Fishes. 



W. J. MOENKHAUS. 

 [Abstract.] 



During the past three years thirty-three different crosses were made 

 among fishes. ^lost of these were between marine species; several were 

 between fresh-water species, and three between marine and fresh-water 

 species. In no combination was there a failure of impregnation. The 

 per cent, of eggs impregnated was usually large— 50 to 100 per cent.; in a 

 few instances as low as 1 per cent. This per cent. boi"e no relation to the 

 blood relationship of the species. In most of the cases there was either 

 no polyspermy or the per cent, of polyspermy was small. In two crosses 

 this was as great as 50 per cent, of the impregnated eggs. The degree of 

 polyspermy bore no relation to the nearness of relationship. 



In all cases of normal impregnation the earlier phases of development 

 were passed through normally. All crosses except where BatracJius tau 

 was used as the female, the development went beyond the segmentation 

 stages, the embryonic shield being apparently perfectly formed. Many 

 crosses went beyond this to the closure of the blastopore, but in these 

 cases the embryo was varyingly shorter than the normals. Seven crosses 

 developed into healthy fry. Some of these, however, showed abnormali- 

 ties, usually in the caudal peduncle and the anal fin. These latter crosses 

 were either between species of the same genus or nearly i-elated genera. 



