High and low Dimorphisra. 325 



them. Furthermore it sliould be observed that the comb of the small 

 chela is very large compared to that in the large chela. 



We have now to trace our series among the allied species. 

 Firstly there is a form described by Dollfus (10), L. Corsica which 

 measures 5 mm., and he says in relation to the male: "La forme 

 bien plus allongée des chélipèdes chez le male paraìt cependant un 

 caractère distiuctive assez net." So we may conclude that this form 

 besides being- large is also high in regard to the chela. This is the 

 only species of Leptochelia which is known to be larger than L. 

 dubia. Passing to the smaller forms, the nearest is L. inermis (Doll- 

 fus) which measures 2 — 6 mm. This species has the chela in the male a 

 good deal reduced, but the two tubercles are recognizable as such 

 on the lower arm of the forceps. Compared to L. dubia therefore it 

 is about middle-sized, and we see that it is low in respect to the 

 chela. The uropod of tbis species has 4 joints in the endopod and 

 one in the exopod; i. e. it is in a state comparable to the develop- 

 mental stage of the uropod of L. dubia tìgured in Piate 20, Figs. 15 

 — 17. The next species in the series is L. mercantilis (see Appendix 

 page 335 and Figs. 18 — 23). The male measures 1 — 5 mm., the female 

 being larger 2.75, but the reduction in size of the male is the im- 

 portant point for us. Corresponding to this reduction we see that 

 the cheliped is greatly reduced in size, being assimilated in its pro- 

 portions to that of the female, while the two tubercles have become 

 eompletely fnsed to form a continuous serrated ridge (Fig. 21). The 

 chela comb is largely developed, and the antennae bave long sen- 

 sory hairs (Fig. 20) two characters which we saw beginning in the 

 low males of L. dubia. Finally the uropod has the endopod 4-jointed 

 and the exopod one-jointed (Fig. 23). Meantime the female of this 

 species (Fig. 19) has not deviated in the least from the female of 

 L. dubia, except that it is a little smaller and has quite constantly 

 only 4 joints in the endopod of the uropod, when adult and oviferous, 

 whereas the female L. dubia as constantly has 6 when adult, though 

 in a developmental stage it passes through the 4-jointed condition 

 of the adult in L. mercantilis. The exopod of L. 7nercantilis is 

 stili one-jointed but increased in size (Fig. 23). 



The next species in L. mergeUinae (Figs. 24 — 28). It is very 

 closely allied to the foregoing but dififers in being stili further reduced 

 in size (cf = 9mm., Q 1.3 mm.), and in correspondence the chela of 

 male and female are closely similar (Figs. 26 and 27), the antenna has 

 very greatly developed sensory hairs (Fig. 24), and the uropod has 

 stili further diiferentiated on the same lines as the preceding species, 



