104 MisceUaneous, 



more precisely its true point of departure. Now the Dromidse 

 include three very distinct subfamilies (Homolinse, Drominse, Dyno- 

 meninse), and we are entitled to ask ourselves which of these is the 

 one whence the Dorippidge have sprung. 



The question is not difficult to solve. Almost all the Dorippidae 

 exhibit a lateral line, and in many of them the females are provided 

 with peculiar furrows on the sternal face of the thorax. These two 

 fundamental characters reappear iu the Drominte and in the Dyno- 

 menina?, and since they are absent in the case of the Homolinse, this 

 latter subfamily is de facto set on one side. Again, many Dorippidae 

 have a rostrum which is decidedly triangular in shajje, like that of 

 the Dynomeninae ; moreover, the Palicids, their most primitive 

 group, resemble the latter subfamily in respect of the posterior pair 

 of legs, which alone are modified and brought over on to the back. 

 The Dorippidae therefore are connected with the Dromidae of the 

 subfamily Dynomeninae. 



The adaptive modifications which have transformed the Dromidae 

 into Dorippidfe have essentially affected the respiratory organs. The 

 efferent apparatus has developed in a fairly progressive manner : 

 the two expiratory orifices, which are very wide apart in the 

 Dromida?, have gradually approached one another, and have ended 

 by fusing together into a more or less projecting endostomial furrow 

 on the frontal side. But it has been otherwise in the case of the 

 afferent orifices. Situated at the very base of the anterior limbs in 

 the Dromidtie, sometimes they have undergone reduction until they 

 closed altogether, sometimes they have become enlarged and elon- 

 gated and have assumed the form of a cleft, in which moves the 

 basal joint of the external maxillipeds, with its long epipodite. 

 Hence two subfamilies, two separate series, which also differ one 

 from another in other important characters. 



Among these latter the most typical are those which are connected 

 with the female genital apparatus. In the species belonging to the 

 first series the female sexual aperture has remained at the base of 

 the third pair of limbs, as in the case of the Dromidae ; moreover, 

 the eggs are few in number, of very large size, and certainly pro- 

 duce young differing but little from the adult. In the second series 

 the female sexual aperture has become sternal in position, as in the 

 case of the crabs, while at the same time the eggs, which are nume- 

 rous and small, produce but little advanced larval forms. 1 do not 

 see what relation exists between these two classes of characters ; 

 but as regards the position of the sexual apertures, it is permissible 

 to state that the Dorix^pidae of the first group are far from having 

 completed their evolution, for the Leucosidae, which show great 

 affinity to them, already exhibit these orifices on the sternal face. 



As for the special evolution of the two subfamilies, this appears 

 to me to be closely connected with the dimensions of the ova. 

 "With large eggs, and consequently late hatching, the young are 

 necessarily little different from the adult and badly endowed as 

 regards swimming-power ; the dissemination and, in consequence, 

 the diversification of the forms must be limited. AVith small eggs 



