534 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxviii. 



Since tlio, eo-ii- tu'>t^ i>i secreted only as there is a demand for more 

 space and is (^xtended by the pressure^ of the issuing- eggs, it follows 

 that this pressure, actingahvays along (he axis of the egg tnl)(>, flattens 

 the i'^j^<^ at right angles to that axis. Kach (^^^^^ assumes a biscuit shape, 

 with the exc(^j)ti()n of the one tirst extru(h'd, which is hemispherical. 

 The form is usually fairly synimeti'ical, the pressure being ecpially 

 distributed, but sometimes an agg will get flattened on one side more 

 than the other (see fig. 2). 



The germinal area is about in the center of the proximal side of the 

 biscuit in the great majority of cases. But here again there are excep- 

 tions and occasionally an Qgg is reversed as 

 it issues and the germinal area appears at 

 the center of the distal side. From this 

 \^ I center tlie embryo spreads gradually until it 

 covers the flattened side and extends down 

 ovei' the edge of the biscuit, so that in 

 advanced development the appendages can 

 l)e distinctly seen on the edges of the eggs 

 under a hig'h power (see tig. 35). Not only 

 are the germinal areas thus all upon the 

 center of the proximal sides of the eggs, 

 ])ut the s3'nHnetry is carried still farther in 

 the fact that the longitudinal axes of the 

 end)ryos arc^ very closely parallel. This 

 lu'ings the coi-responding ap])endages of 

 n the different endnyps in longitudinal rows 

 \ along the sides of the Qgg tubes. 

 ^1 The eggs also change in color with ad- 



vancing development. At first colorless or 

 with a yellowish tint, they gradually assume 

 j\ the color of the pigment which is to distin- 

 guish the nauplius when it fiuall}' becomes 



Fig. 35.— I'llRTIO.N (IF .\N K(ili-STKIX(; trCe. 



OF cvLuais BoNiTo. {iiiuHi.Y rpj^j^ ^.^j^^. ^^^.j^^ -^^ dlfiereut spccies and 



is readily visible to the naked eye against 

 a white background for some time previous to hatching. If the living- 

 copepod be placed in a porcelain dish and examined with a hand lens 

 the color shows to good advantage. It is so constant in the same 

 species and so distinct in many of them as to afford a good supple- 

 mentary evidence of identit}^ in females carrying- f ulh^ developed egg-s. 

 There is no regular breeding season. Females with fully developed 

 eggs are found alongside those with egg strings only partially extruded 

 or with none at all. And oftentimes a single fish will yield these 

 different adult forms and several chalimus stages. But while there is 

 this great irregularity in the breeding season of different individuals, 



