Miscellaneous, fiB 



enveloping membrane. In many Aphides these Amoeboid cor- 

 puscles undergo a further degree of evolution by their transfor- 

 mation into small unequal bacilli, which are straight or diversely 

 flexuose, immobile and colourless, and 0005-0020 millim. in 

 length. We might easily be led to regard them as a parasitic 

 vegetable production, if we had not before our eyes all the suc- 

 cessive phases of the transformation of these elements. More- 

 over their rapid solubility in alkaline solutions constitutes a 

 character which differentiates them completely from the micro- 

 scopic Oscillatorice, with which they present the greatest resem- 

 blance. Several times I have succeeded in seeing some of these 

 corpuscles in the ovarian tubes, or forming small groups at the 

 bottom of the terminal chamber of the ovigerous sheaths. 



In the third and last part of this memoir I shall investigate 

 the phenomena of reproduction in the oviparous Aphides, and 

 show how these are related to the viviparous generations which 

 preceded them. 



MISCELLANEOUS. 



On the Metamorphoses of the Marine Crustacea. 

 By M. Z. Gerbe. 



The author gives the following summary of the conclusions to 

 which his investigations have led him : — ■ 



1 . The larvae of the species belonging to the genera Maia, Pisa, 

 Platycarcinus, Cancer, Xantus, Gonoplax, Portunus, PorcellanOy 

 Palinurus, Homarus, Callianassa, Crangon, Athanas, Palcemon, 

 Mysis, lone, and very probably those of many other genera, undergo, 

 immediately after their birth, a first moult, which gives them a form 

 different from that which they possessed in the egg. 



2. None of the marine Crustacea of the division Podophthalma, 

 or of the Edriophthalma, which I have observed has its organization 

 complete at birth or possesses forms by which it might be referred 

 to the species to which it belongs, and all are furnished with transi- 

 tory appendages for natation, which give them a locomotion different 

 from that which they will have in the perfect state : these appendages 

 persist until the fifth or sixth moult, and become atrophied in posi- 

 tion without falling off. 



3. It is only at the fifth moult in some, and at the sixth in others, 

 and after having undergone modifications at each moult, that the 

 general form of the adult and the external organs are complete. 

 To these transitory external forms, so different from those of the 

 perfect animals, and becoming modified at each moult, are due 

 a multitude of false species and genera and doubtful families *, and 

 even, as regards the larvae of the Palinuri, an entire order to be 

 eliminated. 



* The family of the Erichthidae, in the order Stomapoda, appears to ine 

 to be chiefly founded upon Crustacea in the larval state. 



