1 6 VEOCEEDINttS OF TELE 



stem, than the female, and I am informed by Mr. E. M. Holmes 

 that the male plant is generally found in the more outlyinsj 

 sterile portions of the fields. This suggestive feature may be 

 observed in the common hop, Sumulus Lupulus, in which the 

 female is larger, and the male similarly situated in the more 

 sterile regions. 



If we now take some example from the animal kingdom, we 

 shall find more varied features presented by the male and female 

 respectively, there being far more disturbing influences at work 

 than is the case with the more simple plant. Amongst Eotifers, 

 as, for instance, in BracJiioniis ursularis, the male is often not 

 more than a sixth of the length of the female, and is little more 

 than a locomotive reproductive machine, it having no alimentary 

 canal, and its life of necessity being exceedingly brief, though 

 very active whilst it lasts, being spent in rapidly darting through 

 the water in search of its mate. The eggs from which the male 

 and female respectively emerge are exceedingly diflferent, the 

 male ova being rounded and not more than half the diameter of 

 the oval eggs of the female, and also being five times more 

 numerous. Again in Crustacea, amongst Isopods, we find some 

 extreme differences following the usual rule. In Anceus maxil- 

 laris the male is smaller, with legs far more developed and more 

 hairy than the female, and with powerful predaceous jaws ; in. 

 the female the last three segments of the cephalothorax are 

 greatly distended to lodge the ova, and the mouth-parts are of 

 a simple suctorial character, the limbs being feeble. In the 

 common Bopyrus squillarum, so often found in the gill-chamber 

 of prawns and shrimps, the male is almost microscopic in dimen- 

 sions, less than a millimetre, and spends its life as a parasite 

 attached to near the genital orifice of its relatively gigantic mate, 

 which is about half an inch in length, or about twelve times the 

 length of its partner. There is a curious exception met with in 

 the Isopods, nor am I able to interpret the exception ; it is that 

 of the common Lygia oceanica, in which the male exceeds the 

 female by one third, although the female, as in other Isopods, 

 has not only to carry her eggs, but also her young, when each is 

 about three millimetres in length. In Amphipods the difi"erences 

 between the sexes are often found to be very great, and have led 

 to numerous mistakes, the male being usually hairy and bearing 

 more specialized limbs, probably to assist in grasping the female. 

 For instance, Aora p^acilis is the male of Microdeuteropus 

 anomalus, and Ericlithonus difformis is the male of Dercothoe 

 punctata. In the Decapods a striking example is furnished by 

 Corystes Gassivelaunus (the Mask Crab), the males of which 

 species are far more numerous than the females, their chelae 

 being more than twice the length of those of the females. A 

 still more extreme difference is found in the sexes in certain 

 Cirripeds ; in Scalpellum regium the male is not more than a 

 millimetre in its greatest length, and, having no mouth, it is 



