ii2 ANNALS OF SCOTTISH NATURAL HISTORY 



females. What can be the reason for such a large percentage 

 of male Cyclops ? It was certainly not due to an abnormal 

 abundance of that sex in the ponds at Gullane ; for my 

 own and my son's observation proved that males were not 

 unusually numerous, compared with the number of females 

 present. Our experience tends rather to show that in tow- 

 net collections males are usually in the minority. It 

 becomes necessary, therefore, to seek some other explanation 

 of the remarkable difference in the percentage of the two 

 sexes ; and probably the most satisfactory explanation is to 

 be found in the difference in the structure of the anterior 

 antennae of the male and female. In the male, both of the 

 anterior antennae are modified for grasping, being distinctly 

 hinged near the middle as well as near the end ; they can, 

 therefore, at the will of the animal, be bent or folded over so 

 that the amount of the horizontal extension of the antenna; 

 is very much reduced. The female's anterior antennae are 

 not hinged in the middle ; and when the animal is swimming 

 they are always extended at, or nearly at, right angles to the 

 axis, of the body. The female is likely, in this way, to meet 

 with greater obstruction than the male when attempting to 

 enter the door of this natural trap. Whether the above 

 explanation is sufficient to account for the large percentage 

 of male Cyclops captured by the utricles, or whether the 

 difference is due to other causes, the fact that there is such 

 a difference is of interest as indicating the influence such 

 plants possess over the destinies of these lowly organisms in 

 their struggle for life. 



When we come to the question of the great preponderance 

 of Ostracoda over all the other organisms observed in the 

 utricles, we find the explanation much easier. 2528 speci- 

 mens of Ostracoda were obtained in the 800 utricles ; and 

 they nearly all belonged to two species, Cypria Icevis 

 (O. F. Muller) and Cypria serena (Koch), which, from their 

 active habits, small size, and globose form, could more easily 

 make their way into the Utricularia-traps than any other 

 Entomostracan inhabiting the ponds. A few specimens of 

 Cypria opJithalmica (J urine) a somewhat larger species, and 

 much compressed in form were the only other Ostracods 

 observed. 



