212 PRIMARY FACTORS OF ORGANIC EVOLUTION. 



over the series of nauplius forms [which are traversed 

 by other copepods] and the larva, as soon as hatched, 

 undergoes a moult, and appears at once in the youngest 



Cyclops form with 

 antennae adapted 

 for adhering, and 

 mouth - parts for 

 piercing. From this 

 stage they under- 

 go a retrogressive 

 metamorphosis, in 

 which they become 

 attached to a host, 

 lose more or less 

 completely the seg- 

 mentation of the 

 body, which grows 

 irregular in shape, 

 cast off their swim- 

 ming feet, and even 

 lose the eye, which 

 was originally pres- 

 ent {LerncBapoda). 

 The males, how- 

 ever, in such cases 

 often remain small 

 and dwarfed, and 

 adhere, frequently 

 more than one, 

 firmly to the body 

 of the female in the region of the genital opening. In 

 the Lernaa such pigmy males were for a long time 

 vainly sought for upon the very peculiarly shaped body 

 of the large female (Fig. 52), which carries egg-tubes. 



Fig. 52. — LerncEa branchialis ; a, male ; ^, non- 

 degenerate female ; c, female after fertilization 

 undergoing metamorphosis ; d, do, with egg sacs, 

 natural size. From Glaus. 



