192 CARL L. HUBBS. 



these embryos is seemingly largely effected over the surface of 

 the body and fins, especially in the highly elevated vertical fins, in 

 the distal dermal flaps of which the large interradial vessels form 

 an extensive capillary net-work (cf. Ryder, 1885, 1893). The 

 embryos, thus supplied with food and oxygen, pass through their 

 development in the ovary, lying tightly packed against the ovarian 

 walls and ovarian sheets, some directed forward, others back- 

 ward, in such a fashion, as Agassiz long ago pointed out, as 

 greatly to conserve space. 



About the time of birth, the young of Amphigonopterus (and 

 of other embiotocids) undergo a notable change, which may be 

 termed the natal metamorphosis. The body becomes thicker, the 

 flesh firmer ; the vertical fins become shorter and less flexible, 

 the interradial vessels smaller, the dermal flaps obsolete, and the 

 hind gut more nearly normal in structure. The scales have al- 

 ready developed so far that they are widely imbricate, and the 

 chromatophores have been formed in large numbers, but the body 

 even in the largest embryos is very much paler in color than in 

 the newly born young, particularly the males, which are even 

 darker than the adults. In other species, as Enibiotoca lateralis, 

 and Hypsitnis caryi, the latter as described by Agassiz, a sharply 

 defined color pattern is developed before birth. The viviparous 

 perches thus lose nearly all traces of embryonic peculiarities im- 

 mediately before and after birth. 



The young of Amphigonopterus aurora at birth vary in length 

 approximately from 30 to 35 mm. (the caudal fin excluded), 

 being about one third or one fourth as long as their mothers, as 

 in other species of the family. Among several hundred examined 

 early in June, the smallest free-swimming young was 29.0 mm. 

 long, the longest unborn embryo, 35.5 mm. In a given series of 

 embryos from one female, the variation in length is seldom more 

 than one or two millimeters ; thus the two sexes in Amphigonop- 

 terus are seen to be of at least approximately the same size at the 

 time of birth ; the differential rate of growth is wholly, or almost 

 wholly, postnatal. 



A female of Enibiotoca lateralis, 257 mm. long to caudal, 

 caught near Piedras Blancas, California, on June 2, contained 26 

 young 46 to 49 mm. long, not quite ready for birth. A slightly 



