( ■' ) 



by the modified coxopodites of the 5th pair of thoracic legs of the male, 

 or by the protruded vas deferens itself; but more often no special means of 

 fertilization are discoverable. 



The extruded ova, which are usually small and numerous, but fin some 

 of the sublittorai species) may be few and large, are attached to the setose 

 biramous abdominal appendages of the mother. In a few herm.it-crabs there 

 grows out from the side of the abdomen of the female a fleshy or membra- 

 naceous fiap that acts as a brood-pouch: this, like the abdominal appen- 

 dages, is placed on the left side, except in the unique Paonropsis, where it 

 may be on either side. 



The larva is hatched as a bilaterally-symmetrical zo3ea, not unlike the 

 zoaea of some of the macrurous Decapods in general form. It has a rostrated 

 carapace, and an elongate and normally-extended, segmented abdomen, and 

 all the appendages from the eyes to the 3rd maxillipeds are represented, the 

 first two pairs of maxillipeds being the principal organs of locomotion.* 



In the course of successive moults the remaining thoracic appendages 

 appear and, ultimately, five pairs of abdominal appendages (somites 2 — 6) also, 

 the larva, which is now known as aGlaiicothoi', being still bilaterally symmetri- 

 cal, except that the cheliped of one side may be enlarged. 



If, as is generally the case, the young hermit-crab now takes up its abode 

 in the shell of a gastropod moUusk, the appendages of one side of the abdo- 

 men — usually the right — become atrophied. 



For the details of the post-embryonic development of Paguridse, the following papers 

 should be consulted : — 



Philippi ;— Zoc von Pagurus : Archiv fur Naturges. VI. 1840, p. 184, pi. iii, fig. 7, 8. 



Rathke ; Zur Entwickelungs. der Decapoden : Archiv f. Nat. VI. 1840, p. 241. Trans, 

 in Ann. Mag. Nal. Hist. VI. 1840, p. 263, 



Spence Bate; Carcinological Gleanings, No. IV.: Ann. Mag. Nat. Hisl. (A) II, 1868, 

 p. 114, pi. ix, fig. 2. 



Boas ; Vid. Selsk. SUr., 6 Raekke, Nat. og Math, Afd. I. 2. 1880, p. 197 

 Faxon: .Mem. Mus. Comp. Zool. Harvard, l.\. No. 1, 1882, pi. .\ii, fig. 20-30, pi. xiji, Ho. 

 1—9. 



Sars : Decapod. Forvandlinger : .4rch. f. Malk. o Nat. .Xlll. 1890, pp. 135 —161, pi. i— iii. 

 Bouvier: Ann. Sci. Nat. Zool. (7)X11. 1891, ^p. e,5—&2 [ubi lit. pleii.) 

 Borradaile: in Willey's Zoological Results, Part V, 1900, pp. 585 590. 



5. Habits and Mode of Life. 



There is no group, even of Crustacea, that outdoes the Paguridea in 

 combining uniformity of structure with diversity of habit. Morphologically 



•This summarised statement applies only to the Pagurolds ; in the Lithadida, according to Boas and 

 G. O. Sars, the larva leaves the et;g in a still more advanced stage. 



