IDYIA. 33 



however, for it often attacks a Bolina or Pleurobrachia as large 

 or even larger than itself, when it extends its mouth to the ut- 

 most, slowly overlapping the prey it is trying to swallow by fre- 

 quent and repeated contractions, and even cutting off by the 

 same process such portions as cannot be forced into the digestive 

 cavity. 



The general internal structure of the Idyia corresponds with 

 that of the Bolina and Pleurobrachia ; it has the same tubes 

 branching horizontally from the main cavity, then ramifying as 

 they approach the periphery till they are multiplied to eight in 

 all, each of which gives off one of the vertical tubes connected 

 with the eight rows of locomotive flappers. Opposite the mouth 

 is the eye-speck, placed as in the two other genera, at the centre 

 of a small circumscribed area, which in the Idyia is surrounded 

 by delicate fringes, forming a rosette at this end of the body. 

 These animals are exceedingly brilliant in color ; bright pink is 

 their prevailing hue, though pink, red, yellow, orange, green, 

 and purple, sometimes chase each other in quick succession along 

 their locomotive fringes. At certain seasons, when most numer- 

 ous, they even give a rosy tinge to patches on the surface of the 

 sea. Their color is brightest and deepest before the spawning 

 season, but as this advances, and the ovaries and spermaries are 

 emptied, they grow paler, retaining at last only a faint pink tint. 

 They appear early in July, rapidly attain their maximum size, 

 and are most numerous during the first half of August. Toward 

 the end of August they spawn, and the adults are usually de- 

 stroyed by the early September storms, the young disappearing 

 at the same time, not to be seen again till the next summer. It 

 is an interesting question, not yet solved, to know what becomes 

 of the summer's brood in the following winter. They probably 

 sink into deep waters during this intervening period. The Idyia, 

 like the Pleurobrachia, moves with the mouth upward, but in- 

 clined slightly forward also, so as to give an oblique direction to 

 the axis of the body.* 



* Until this summer only the three genera of Ctenophorae above mentioned were 



supposed to exist along our coast, but during the present season I have had the good 



fortune to find two additional ones. One of them, the Lesueuria, resembles a Bolina 



with the long lobes so cut off, that they have a very stunted appearance in compari- 



5 



