Chap. III. GENUS IDYIA. 273 



the contents of these organs were emptied, they grew again paler and paler, and, after 

 the eggs and spermatic particles had been entirely discharged, the spherosome itself 

 faded and assnmed a livid, ^lale, grayish color, only a slight tinge of pink remaining. 

 The first September storms broke them all to pieces, and nothing could be found 

 afterwards but floating fragments. This year I have found them again in great 

 abundance, and, as before, they made their first appearance early in July. Several 

 years ago, in 1852, I had also an ojiportunity of seeing large numbers of them 

 m the harbor of Provincetown on Cape Cod, in the month of August. They had 

 reached about half the size of tliose seen later, and had probably made their 

 ajjpearance not long before. Afterwards I traced them as far north as the Bay 

 of Fvmdy, always lai^ger in proportion as the season advanced. But I have never 

 seen them during the winter or in early spring. A careful search, however, made 

 this year by my son, from the beginning of August to the first week of September, 

 led him to the discovery of a large number of young, barely visible to the naked 

 eye. They grew gradually larger; but after the first September gale the young 

 disappeared with the adult, which, as I have already stated, break into fragments 

 in our heavy September storms. The young, of course, must survive ; and the ques- 

 tion arises, what becomes of them during their temporary disappearance, on the 

 approach of the winter, until the following summer? I can find only one explanation 

 for this phenomenon, suggested by the habits of the adult. 



I have already stated, that in the summer months our pretty Idyia appears in 

 great quantities at the surface of the water during the hottest hours of the day. 

 In the morning and evening they are not visible, but as the sun rises above the 

 horizon they may be seen deep below the surface, betrayed by the iridescent 

 colors of their locomotive flappers, and slowly ascending until about ten o'clock, 

 when they are fully in sight near the surface, where they appear in all their 

 beauty. It is thus evident, that these animals may, under different circumstances, 

 voluntarily rise to the surface of the water or dive into the deep ; and the nature 

 of the circumstances so influencing them is plainly indicated, not only by the fact 

 that the warmest hours of the day bring them to the surface, but also by the 

 fact, ascertained with equal certainty, that the slightest ripple upon the surface, 

 hardly producing perceptible agitation of the water, is sufficient to cause their instan- 

 taneous disappearance, and that they remain out of sight for days in succession when 

 the sky is overcast or the weather chilly. What can be more natural therefore 

 than to assume, that the adult Idyias, having performed their part in life, break 

 up under the influence of the waning summer ; while, during the whole winter, the 

 young do what their parents have been doing at intervals during the summer, that 

 is, subside into deep waters, to reappear only with the more genial season, when 

 they complete their growth, reproduce their kind, and die in their turn. 



VOL. III. 35 



