HARDWICKE'S SC lENCE -GOSSIP. 



229 



tioned he believes had not been hatched from the 

 eggs more than six weeks, and very likely a shorter 

 time. How long the young retain their free 

 swimming habits after arriving at the lobster-like 

 form was not ascertained. Specimens three inches 

 long have acquired nearly all the characters of the 



of their development do they have all the decapodal 

 legs furnished with natatory exopodal branches. 

 They are undoubtedly larval forms closely allied to 

 those of Homarus in some of the groups of the 

 Macrourans, although they appear"', to be as yet 

 unknown. 



Fig. I6l. Third larval stage of Lobster (nat. size i in. long}. 



adult. " Of all the larval stages of other genera of 

 Crustacea, there are none which are closely allied 

 to the early stages of the lobster. According to 

 Eathke, Jstacus leaves the e^g in a form closely 

 resembling the adult, the cephalo-thoracic legs 



Fig. 162. Terminal portion of abdomen of ditto, x 15 dia. : a, 

 one of the spines of the posterior margin of terminal seg- 

 ments, X 75. 



having no exopodal branches, and the abdominal 

 legs being already developed. Of the earlier stages 

 of the numerous other genera of Astacidea and 

 Thalassiiiidea scarcely anything is known ; but as 

 far as is known, none of them appear to approach 

 the larvse of the lobster. Most of the species of 

 Crangonid(B and Palcemonidte (among the most 

 typical of Macrourans) of which the development 

 is known, are hatched from the Qgg in the zoi-a 

 stage, in which the five posterior pairs of cephalo- 

 thoracic appendages, or decapodal legs, are wholly 

 wanting, as are also the abdominal legs, while the 

 two anterior pairs of maxillipeds, or all of them, 

 are developed into locomotive organs. In no period 



"Notwithstanding these larval forms of the 

 lobster seem to have no close afiinities with the 

 known larvae of other genera of Macrourans, they 

 do show in many characters a very remarkable and 

 interesting approach to the adult ScMzopoda, par- 

 ticularly to the Mysida. This seems to furnish 

 additional evidence that the Schizopods are only 

 degraded Macrourans, much more closely allied to 

 the Sergestidce than to the Squilloidea." 



Fig. 163. Basal portion of one of the cephalo-thoracic legs of 

 second pair, showing epipodus and branchial appendages 

 X 20 dia. 



Mr. TV. H. Silsbee thinks the lobster only moults 

 once a year, after having nearly attained its matu- 

 rity, at some period between May and November. 

 The length of the animal observed, before moulting, 

 was six and a half inches; immediately after it was 

 seven and a quarter, — a sudden increase of three- 

 quarters of an inch. 



" He woidd be a bold man who would venture to 

 predict where science will be fifty years hence ! " — 

 Huxley. 



