No. .i.|7.J BREEDING HABITS OF CRAYFISH 



transparent look that enables one to out e<;K^ of 

 with ease. Under the lens the ei;L;s present a vc 

 appearance as the surface has ronie lo he eoxeic d 

 cell outlines that form a neat niosau . I lu sc i ells : 



ter become reduced to 50 /x. 



The e-.s are often much fhttuud spin U 



rexoKe in then cases so as t-. k^.p miu t uj 

 cells flatten doun and the ll,<.s u un ^l. 111 mik.mH, 



After this hr.st week there is a period <il apji 

 change, nearly a second week m whu li the e^-s tui i 

 and at first were thought to be dead. 1 lie surhi 

 longer show, while the yolk is ari-aii!;ed m laii;c' polvi 

 about 150 /A in diameter and not (piiie in conuu 

 another. Reagents, however, show the \eiv main 

 of the surface overlying these yolk i)vrainids. 



_ But bcforC the CUcl of this SCIOIH 



embryo is outlined somewhat as in Reicheiilxu li s Si. 

 H ; that is in gastrula stages. 



In the third week Naui)lius stages hke Slai^c 

 of Reichenbach were arrived at m from 18 to 28 davs 

 batches of eggs. Apparently in connection with ih 

 amount ot >olk m these egg^ the embixn is sm dl. 



About the 30th day the embryo had grown 

 of 1000 |Li and was about stage 11 ot Keiehenbaeh, 

 some nine pairs of appendages. Howe\ci om. 

 ing lot of eggs got to that stage in 21 da\s 



rapid lot. Here a difference of temperature was 

 may have caused this unusuallv iai)id de\eli)pmuu 

 exceptional eggs about two (la\s weie spent 111 p 

 stages to H and nine days from 1 1 t(. J. Keiehei 

 stage K was reached 15 days attei J and hate hin; 



In C. affinis we thus found that c]ea\a.i;e took 

 week, the beginning of an embi\<) tlu seo)n<l wti k 

 as far as the Nauplius the third week and nioic, t(. 



