Macrourae or Long-tailed Crustacea. S2S 



discovery of the metamorphosis preceded the knowledge of the 

 major part of the larvae of the Crustacea^ which must otherwise 

 have formed a very formidable group of Shizopoda, well calcu- 

 iated to bewilder future zoologists. 



For the benefit of such zoologists as may wish to witness for 

 themselves the hatching of the ova of the Palcemati, it may be 

 observed, that the females, which are vastly more numerous than 

 the males, carry their ova attached in groups to the inner branch 

 of the subabdominal fins, and that these ova are at first of an 

 oval figure, a pale yellowish-brown colour, and small size, but 

 that as they increase in size they become more round, change to 

 dark brown, then to reddish-brown, acquiring gradually greater 

 translucency, and a pale flesh colour, with black eyes. Females 

 arrived at this stage of gestation, being kept in frequently re- 

 newed sea water for a few days, will assuredly confirm what I 

 have above stated. 



EXPLANATION OF THE FIGURES IN PLATE L 



Fig. 1. Larva of Prawn {Pakemon serratns) when first hatched ; a, of the na- 

 tural size, and b magnified. A side view of rostrum, c. One of its 

 cleft members more magnified, d. 



2. Intermediate stage of the same ? Natural size, a, and magnified, b, 



3. Supposed last stage of the larva of the Prawn. Natural size, a, and 



magnified, b. 



4. Another sketch of the fore-part and tail of the same. A natatory di- 



vision of the Pedimanillee^ a. b, c, Do. of the two chelate members. 

 d, Cyf^ Do. of the three posterior members. 



5. One of the second pair of chelate members more highlj magnified. 



Considerations respecting a New Power which acts in the For- 

 mation of Organic Bodies. By M. Beezelius. 



When new compounds are formed in unorganized substances 

 in consequence of action between different bodies, it is the result 

 of the mutual tendency of these bodies to comply, in a more per- 

 fect way, with their affinities. On the one hand, those substances 

 whose affinities are the strongest combine ; and, on the other, 

 those which have the weaker affinities are expelled. Previous 

 to the year 1800, it was not supposed that any other determinate 



q2 



