220 Miscellaneous. 



with those of any age when they moult and are too numerous in a 

 small space. 



I have also observed that temperature exerts a marked influence 

 upon the duration of the incubation of the eggs and upon the num- 

 ber of the periodical moults. The number of moults is eight in the 

 first year following exclusion ; it is five in the second year, or six 

 in those years when the temperature is high ; it is from two to 

 three in the third year, which makes from fifteen to seventeen 

 moults in all to the commencement of the fourth year. The male 

 crayfish becomes adult (that is to say, ready for copulation) on en- 

 tering upon his third year ; and the female is ready for fecundation 

 at the commencement of the fourth year. 



All naturalists are aware that the organs of the crayfish are re- 

 produced. According to my experiments the antennae push out 

 again during the time which separates one moult from the following 

 one. The other limbs (such as the claws, the legs, the false legs, 

 and the lamellae of the tail) are regenerated more slowly, three moults 

 taking place during their regeneration. "When the fourth moult 

 comes on, the regenerated limbs have acquired all their strength. 

 In the first year of their existence, seventy days suffice for the re- 

 generation of these limbs in the young crayfish. This is not the 

 case with the adidt crayfish : the female requires three or four years 

 to reproduce its limbs, and the male from a year and a half to two 

 years ; for the adult male moults twice a year, and the adult female 

 only once. 



In an early note I will make known the results of experiments 

 of this kind relating especially to the regeneration of the eyes. — 

 Comptes Rendus, July 17, 1871, tome Ixxiii. p. 220. 



On Hypocotyledonary Gemmation. By Prof. Asa Grat. 



My attention has been called, by Mr. Guerineau, the gardener 

 of the Cambridge Botanic Garden, to a remarkable instance 

 which occurs in all our seedlings of Delphinium nudicauU, the 

 unique red- or red-and-yellow-flowered species of California. As 

 this species is now in European cultivation, and probably a variety 

 of it, D. cardinale, was raised and figured in England several years 

 ago, the peculiarity in question is likely to have been noted ; but I 

 have seen no account of it. In germination the slender radicle 

 elevates a pair of well-formed ovate cotyledons in the usual way. 

 These acquire full development : but no plumule appears between 

 them ; consequently the primary axis is here arrested. Soon a 

 uapiform thickening is formed underground at the junction of the 

 lower end of tlie radicle willi the true root : from this is produced a 

 slender-petioled :i-lobed leaf, which comes up by the side of the 

 primary ])lantlet ; soon a second leaf appears, and so on, setting up 

 the permanent axis of the plajit from a bud which thus originates 

 from the very base of a well-developed radicle, if not from the root 

 itself. ^Silliman's AmcriccDi Journal. July 1871. 



