LIFE-HISTORY OF AMPHIGONOPTERUS AURQRA. 193 



larger female, 265 mm. long, collected in the same pool, also con- 

 tained 26 young, but these were larger, 50 to 54 mm. long, and 

 similar to recently born young obtained near Piedras Blancas, Pt. 

 Sal and Pt. Arguello. Another female of this species, 200 mm. 

 long and 125 mm. deep (exclusive of fins) contained only ten 

 young, 55 to 58 mm. long, some having apparently been already 

 born. The newly born young obtained, all during June, varied 

 in standard length from 43 to 58 mm. A variation in size at birth 

 of at least 16 mm. is thus suggested. Possibly, however, a slight 

 decrease in actual length accompanies the metamorphosis of this 

 species (as in Albnla wipes and the eels). 



In the case of Micrometrus minimus, the extreme lengths of 

 the embryos of a single female were found to differ normally from 

 o.o to 3.0 mm. In three cases, however, the variation was much 

 greater : in one lot of six embryos, the individual lengths were 

 5.5, 9.5, 10.8, 11.5, 14.3, and 14.7 mm.; in a second lot, five were 

 6.6 to 7.6 mm. long, a sixth, 2.7 mm. ; in the third case, all but 

 one of the foetuses were 12.0 to 13.7 mm. long, the abnormal one 

 being 9.0 mm. long, and provided with a strongly sigmoid verte- 

 bral column and a single eye, represented only by a mass of 

 black pigment. Occasionally, a male embryo was found to be 

 slightly larger or smaller than any of its fellows. If the 16 em- 

 bryos in one female, 7 were males 16.3 to 18.7 mm. long, while 9 

 were females 17.0 to 18.0 mm. long; the average as well as the 

 mean length for each sex was 17.5 mm. In another lot of 23 

 foetuses from one female, 10 were males 20.0 to 22.3 mm. long 

 (average length, 21.8 mm.), while 13 were females 20.4 to 23.0 

 mm. long (average length, 21.7 mm.). 



Soon after birth the young of Amphigonopterus aurora leave 

 the lower pools in which they were born, only a few remaining, 

 probably for a very short time, in company with the breeding 

 adults. They make their way thence into the pools accessible 

 only at high tide, in such abundance that these pools, which are 

 usually of small size and shallow, not infrequently harbor aston- 

 ishingly large numbers of these young fishes. Such pools pro- 

 vide a large degree of seclusion from predatory enemies, as well 

 as the warmest available water, in which the rapid growth of the 

 first months may take place. This concentration and segregation 



