660 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



The eggs of A. stizostethH are more nearly spherical, about O.-il mm. 

 in diameter, and are milk white when lirst laid, soon changing to light 

 yellow. In both species the eggs remain smooth till hatched, never 

 showing any crenations. 



The long diameter of the agg becomes the longitudinal axis of the 

 larva, but all the larva^ in the same row are not arranged with their 

 heads in the same direction. Every here and there one will be found 

 reversed so that heads of adjacent ones come together, as is common 

 in the egg strings of the Eucopepods. Curioush' enough in this lot of 

 'inegalops eggs it seemed to be quite regularly the fourth ones which 

 were thus reversed, but probably such regularitj^ was accidental. 



The number of eggs deposited b}^ a single female is given as 100 by 

 Claus (1875) for .1. foliaceona^ and as 400 by ffurine for the same 

 species; as l,!2oo ])y Dana and Herrick (1837) for A. c(ito)<toi7ii, and as 



50 to 300 by Kellicott (1880) for 

 A. i<fl.zosfeh!L 



In the author's experience the 

 largest number obtained from a sin- 

 gle female was l)etween 500 and 600 

 for ^1. <-(itost()iiiI and 65 for^l. mega- 

 lops. But it is probable in the latter 

 case that the females had alread}^ 

 deposited some eggs before being 

 captured, since the ovaries were not 

 more than half full. 



After being deposited the eggs 

 become opaque and no trace of the 

 development can Ijc seen through 

 the jelly envelope until two or three 

 weeks before hatching, when the 

 The egg then rapidly clears and it 

 can be plainh^ seen that the body of the larva is folded upon itself, 

 the abdomen and the posterior thorax being turned forward along 

 the ventral surface of the head thorax, while the legs are folded for- 

 ward and inward with the long rowing seta? crossing one another on 

 the mid line (tig. 3). 



The time required for hatching varies greatly, xn A. fol Ulceus it is 

 given as about four weeks (Claus), and as thirty-tive days (Jurine): it 

 is nearly the same for A. catostoi/i/\ thirt^^-live daj's (Dana and Her- 

 rick), and from tw^enty-eight to thirty-five dnxi^ in the author's 

 experience. 



This time proves to })e a sort of golden mean in Argulus develop- 

 ment, other species varying from it in both directions. The period 

 for ^1. amerlcanus is oid}' al)out half as long. Eggs which were laid 

 on June 7, 1902, and which were sent to the author by Professor Reig- 

 hard from the U. S. Fish Commission station at Ann Arbor, Michi- 



•A OF AKtU'LUS ME(;. 

 READY TO HATCH. 



LOPS JUST 



black eyes first become visible. 



