548 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxvih. 



attached the young- to her own bocty, in order to render them material 

 assistance. He describes the "filet" which fastens the embryo to its 

 mother, and designates it as the "cordon frontal. 1 ' It is long and 

 flexible enough to allow the young an independent action and to 

 permit it to apply itself to the fish upon which both the mother and 

 the young live. 



It is a very curious and interesting spectacle, says Hesse, to see 

 these embryos, especially those of Trebius and Caligus, which swim 

 with considerable facility, following the evolutions of their mother, 

 like a small boat towed by a large ship. This liason of the two indi- 

 viduals ceases as soon as the young are able to procure their own 

 nourishment, the rupture taking place about the time of the second or 

 third moult. 



This idea of voluntas attachment was strong^ denied by Ger- 

 staecker and Nordmann, while Stein, who wrote six years before Hesse, 

 and whose work the latter entirely overlooked, also contended that 

 such attachment is purely accidental. That this is the true interpreta- 

 tion is evident from many considerations. 



In the first place the larvae hatch as free-swimming nauplii, posi- 

 tively heliotropic, and therefore frequenting the surface, while most of 

 the fish which are to serve as their hosts live at or near the bottom, as 

 alreadjr noted. We have also seen that the larvas moult at least three 

 times before entering the chalimus stage, leaving the surface and 

 becoming negatively heliotropic after the second moult. Hence each 

 of them must seek out its own host, and there is not one chance in a 

 thousand that it will find the same host upon which it was born. 



And the probability of finding its own mother still upon that host 

 would be even less. Indeed the finding of its own mother under any 

 circumstances after a free-swimming period, no matter how short that 

 period might be, presupposes, if the union is to be voluntary, an 

 ability on the part of either mother or offspring to recognize the 

 other! Such recognition would be at least an anomaly among parasitic 

 Crustacea. 



But even if we grant that the larva might find its own mother, still 

 the act of attachment can not be performed by the latter; it is wholl} T 

 the work of the larva itself, as we have just seen, and must be con- 

 trolled by instinct. And it could hardly be claimed that instinct guided 

 the larva to the body of its parent, since this would necessitate some 

 advantage to result from the union. Such an advantage would be 

 difficult to prove, and even if it were established we should still have to 

 explain the fact that only one or two larva? out of thousands followed 

 their instinct and availed themselves of the advantage. We can only 

 conclude that such a union by no means proves a close relationship 

 between the adult and the larva; that it is purely accidental and of 

 rare occurrence. 



