FARAISITW COPEPODS— WILSON. 335 



In the first place the only reason which he can give for regarding 

 the adult as the mother and the larva as her offspring is the fact 

 that the latter was attached to the carapace of the former. The 

 absurdity of dra\\dng such a conclusion from this single premise has 

 been already sho\vai° and may be briefly restated as follows: When 

 first hatched the nauplii swim freely at the surface; after two or 

 three molts they seek out a suitable host and attach themselves to 

 it. There is not one chance in a million that they will find the 

 same host again, to which their mother is attached, and still less 

 chance of finding the mother herself among other parasites of the 

 same and different kinds. In fact, to find the mother at all neces- 

 sitates the assumption of the ability on the part of the larva or the 

 mother, or both, to recognize the other, which one hardly cares to 

 concede. 



Again, the individual to wliich this larva was attached, and which 

 Hesse calls the ''mother,"' is unfortunately of the male sex, as is 

 clearly shown by Ms figures and description. It has the typical 

 Nogaus form ; there are no signs of dorsal plates on thorax or genital 

 segment, and none of the swdmming legs show any signs of degenera- 

 tion. This fact renders any close relationship between the two 

 practically impossible. 



Finally, Hesse WTites that tliis larva was 3 millimeters long and 1 

 millimeter wide, wdth a fully developed frontal filament. But he 

 describes and figures only a single pair of smmnfing legs, and they 

 are on the second thorax segment. Every metanauplius which has 

 thus far been observed possesses at least two pairs of these swim- 

 ming legs, and a chalimus 3 millimeters in length belonging to any 

 of the subfamilies of the Caligida^ must possess at least three pairs, 

 and ought to possess four pairs, of such legs, the first of which would 

 be attached to the ventral surface of the carapace and not to the 

 second thorax segment. Again, the first antennae are represented as 

 attached to either side of the "umbilical button" at the base of the 

 frontal filament. They are half the length of the carapace, two- 

 jointed, and free to their very base; in other words, the chalimus 

 has no frontal plates. The posterior half of the body is cylindrical 

 and five-jointed, the joints diminisliing in size backward. The first 

 of these joints carries the single pair of legs and, in addition, on its 

 ventral surface: 



On remarque, a, rextremite. d'un article femoral, assez long, des lames plates, 

 denticulees sur les bords et garnies de soies, qui sont destinees a favoriser les 

 mouvements de propulsion et de natation, et, de chaque cote de I'anneau suivant, 

 deux lames plafes, denticulees, qui sont consacrees aux memes fonctions (p. G). 



aProc. U. S. Nat. Mus., XXVIII, p. 548. 



