444 TAGE SKOGSBERG 



The jjosition of Cypridina alhomaculata, W. Baird, 1860 a, p. 201, jal. LXXI, fig. 1 is 

 more uncertain. This species was placed by CI. W. MUller, 1912, under the same heading as 

 the two forms just mentioned. On account of the size and shaj^e of the shell and the arrange- 

 ment of the fixing spots of the shell muscles, it does not seem to me impossible that this species 

 may also belong to this family, and that it is most closely related to the genus Cyclasterope. 

 Relations <-/ the juiir It seems stiU too early to give an opinion as to the mutual relations of the four genera 



dealt with above. It can, however, be said with a fair degree of certainty that Cydasterope and 

 Cycloleberis are comparatively closely related to each other. The genus Asterope, on the other hand, 

 occupies a comparatively isolated position. The same thing may also be said of the genus Asteropternn. 



genera iiwitl toned 

 ahov 



OecoltHjij of reprtid'uciion: — As in the case of the sub-family Cypridininae extremely 



little, or perhaps it would be more correct to say nothing at all, is known of the phenomena 



connected with the oecology of reproduction in this family. I myself can unfortunately contribute 



very little to tlu^ solution of this problem. 



No restricted AH the facts Seem decidedly to support the view that in this family as well breeding is 



iree, ing poioi . ^^^^ limited to a more or less short period but takes place during the whole year. 



The method of breed- When Working at the material of the genus Asterope, so rich both in individuals and in 



the "eni'is ■I'^tcrune? spccies, ou wliich the present work is based, it was very striking to notice how exceedingly rare 



the males were among the mature specimens, in most species they were even quite missing. 



In investigating the last larval stages I observed, however, that the males and the females were 



about equal in numbers, in some cases the males were even decidedly in the majority (three 



to one); cf. A. Grimaldi, below. G. W. MOLLER had precisely the same experience previously 



(1894). As an explanation of this phenomenon he assumes (p. 13) that the males could escape 



the net owing to their superior powers of movement. ,,Eine andere Erkliirung scheint mir 



kaum zuliissig'' .... 



I cannot say for certain whether this explanation is correct. One m a y, however, 

 imagine another explanation, which seems even more jDrobable. This is that we have in these 

 forms an oecology of reproduction which agrees with that which has been observed in the genus 

 Philomedes. In other words after the last larval moult males and females live for a shorter or 

 longer period planktonically. During this planktonic life copulation probably takes place. 

 After copulation both sexes return to the bottom, the males dying comparatively soon after- 

 wards, the females returning to their burrowing or digging life. It is probable that the planktonic 

 life is longer in the case of the males than in the case of the females. 



The fact that on several occasions these forms were found in plankton strongly supports 

 the assumption of a planktonic copulation. I have myself found a male (undescribed) in the 

 plankton material collected by the Swedish South Polar Expedition. G. S. Brady, in his 

 work 1868 a, p. 128 mentions that both A. Mariae and A. teres were caught planktonically, 

 ,, though never very abundantly". The same author adds: ,,It would seem, indeed, that these 

 animals do not ccjme to the surface except after sunset". The same author mentions, 1898, 

 p. 431, that males of A. australis were caught ,, abundantly" in plankton in ,,Otago Harbour". 

 But females seem also to have occurred in the find in (lucstioii, as is indicated by the following 



