12 A REVISION OF THE ASTACID.E. 



Types of six of Le Conte's species (tlescribed in lSO-3) are preserved in 

 the Academy of Natural Sciences of Philadelphia : A. tronloihjtes, A. spiciilifcr, 

 A. fossarimi, A. atigitstatus, A. laiimauus, and A. xdremi. The Museum of Com- 

 parative Zoology also possesses types of ^1. iroyhdyics, A. spimlifer, A.fossn- 

 rum, A. lalimamis, and A. advena. A. fossaruni is not separable from A. Ivoglo- 

 djjies. Le Conte's A. maniculutus remains yet unknown. (See p. 29.) 



The Two Forms of the M(dcs. — In every species of Cambarus, of which 

 many specimens have been examined, two forms of the adult male have 

 been found, characterized by striking differences in the conformation of the 

 sexual parts. In the form called the first by Dr. Hagen, the external organs 

 peculiar to the male are more perfectly formed than in the " second form," 

 where they have somewhat the shape seen in tlie young male. The pecu- 

 liarities of each of these forms have been fully described by Hagen,* to 

 whose monograph the reader is referred for details. No intermediate con- 

 ditions between these two forms exist, and there is no fixed relation between 

 them and the size of the individual, males of the second form being often 

 larger than those of the first, or vice versa. They cannot, then, be consid- 

 ered developmental stages. Dr. Hagen interpreted the facts as a case of 

 dimorphism, and surmised that the second form males were sterile indi- 

 viduals ; but I have since shown that males of the first form after the breed- 

 ing season may revert to the second form by moulting.f , The two forms 

 of the male Cambarus, instead of being dimorphic forms, are probably alter- 

 nating conditions in the life of one individual, the first form being assumed 

 during the pairing season, the second form during the interval between 

 the pairing seasons. The second form is probably impotent ; the testes are 

 smaller than in the first form, the vasa deferentia shorter,^ but I have had 

 no opportunitj^ as yet to examine their microscopic structure. 



Indications of Hennuphruditisni in Cambarus. — Perhaps the only recorded 

 case of undoubted hermaphroditism in the Decapod Crustacea is that of the 

 lobster {Ilomanis ridf/aris) described and figured by F. Nicholls in 1730.§ In 



» Pages 21, 22. 



f On the So-called Dimorpliism in tlic <5enus Cambarus, by Walter Faxon, Amcr. Jour. Sci., Vol. 

 XXVII. pp. 42-4i, January, 1S84.. 



{ See Hagen's Plate II. 



§ An Account of the Hcrmapliroditic Lobster presented to the Royal Society by Mr. Fisher, examined 

 and dissecled, by F. NiehoUs. Philosoph. Trans. Roy. Soc. London, Vol. XXXVI. No. 413, p. 290, 1730 

 (Abridgment, Vol. VII. Pt. III. p. 421, PI. IV., 1734). For a general account of hermaphroditic and other 

 anomalous conditions among the Crustacea, see Faxon, On Some Crustacean Deformities, Bull. Mus. Comp. 

 Zool., Vol. VIII. No. 13, ISSl 



