44 



G. O. SÅRS. 



[No. 1. 



G. Propagation. 



The propagation of the present Phyllopod is very different 

 from that of all other known Phyllopoda, whereas it agrees exactly 

 with that observed in the Cladocera. As in the latter forms, it is 

 performert during the favourable season solely by unfertilized thin- 

 shelled germs, — the so-called summer-eggs, - which are rteposited 

 within the dorsal part of the shell, where these ova immediately 

 develop to yonng of much the same appearance as the adult animal. 

 Having reached maturity they propagate in the same man- 

 ner, and so on for numerous generations. At last, however, 

 when the physical conditions become less favourable, male spec- 

 imens are developed, and then a true sexual propagation takes 

 place, the fertilized ova being in all probability not developed 

 un til a later period, when the conditions again become favourable 

 for parthenogenetical propagation. In the genus Estheria, the 

 latter kind of propagation would seem never to take place, as 

 male specimens are constantly found in company with the 

 female, but little if at all inferior in number; and the ova are 

 thus most probably all fertilized and never found developing 

 while still within the shell of the parent animal. In the genus 

 LinwacJio, on the other hand, a true parthenogenesis has been 

 found to exist, the male sex of our indigenous species- J beiri^~as 

 vet wholly unknown. But the ova in this form do not at all 

 exhibit the character of „ summer-eggs". being invested with a 

 strong peculiarly-formed capsule, and are never found developing 

 within the shell, but at intervals are left deposited in the mud 

 and not hatched till a much later period. 



As to the mode in which the sexual propagation is per- 

 formed, and in what manner the fertilized ova are deposited, 

 I eannot, I am sorry to say, state anything with certaini/, having 

 as yet had not opportunity of watching the animals during this 

 stage of their existence. 



