History of British Eidomostraca. 



315 









Total — each 









No. 



Time employ- 



laying suppos- 









of lay- 



ed for these 8 



ed to be of 40 



Subtract for 



Females re- 





ings. 



layings. 



young. 



males. 



maining. 



1. mother 



8 



From 1st Jan. 

 to end of Mar. 



320 



80 



240 



1. family, of fe- 

 males 240 



8 



From 1 st Apr. 

 to end of June. 



76,800 



19,200 



57,600 



2. family, offe- 

 males 57,600. 



8 



From 1st July 

 to end of Sep. 



18,432,000 



4,608.000 



13,824,000 



3. fam. of fem. 

 13,824,000. 



8 



From 1st Oct. 

 to end of Dec. 



4,423,680,000 

 4,442,189,120 



1,105,920,000 



3,317,760,000 





1,110,547,280 



3,331,641,840 



A single copulation suffices to fecundate the female for life. 

 The male seems very ardent in his amours. By way of prelude, he 

 seizes hold of the hinder feet of the female with his antenna, which 

 being furnished at its extremity with the hinge joint, already de- 

 scribed, forms a fastening round her feet which she cannot unloosen 

 by any exertion — and thus he is carried about with great rapidity 

 for some time. The female, however, at length stops, wearied by 

 her exertions, when the male seizes the favourable moment, and in 

 the twinkling of an eye (as Jurine expresses himself) makes a dou- 

 ble copulation — one on each side. According to MuJler, the male 

 organs are situated in the swellings which we perceive in one or 

 both antennae of that sex, and which are characteristic of it. Car- 

 ried away by the analogy of the Arachnides, and seeing the male 

 seize hold of the lower part of the female with his antennae, he im- 

 mediately conjectured that the organs resided in the swellings which 

 mark the antennae of the male, and were applied to the vulva, 

 which he correctly enough states to be situated in the tail.* This 

 mistake, however, Jurine has cleared up, having shown the organs 

 in both sexes, and watched the act of copulation itself. When the mo- 

 ther is about to lay, we may perceive the material of the eggs, which 

 I have described above under the name of internal ovary, divide in- 

 to two columns, one on each side, and pass through the canalis de- 

 ferens, covered with a fine pellicle, which forms the sac in which 

 the eggs are contained when extruded. This bag of eggs, or exter- 

 nal ovary, remains suspended at the tail of the female for several days, 

 varying from two to ten according to temperature of weather, &c.f 

 The eggs themselves during their sojourn there do not increase in 



* Entomostraca, p. 16-17. 



f Leeuwenhoek says they exclude their ova in the space of one day or night, 



and bring them to perfection in the space of three days (Epist. ad Soc. Reg. 



Ang,) 



