12 A REVISION OF THE ASTACID^E. 



Types of six of Le Conte's species (descril)ed in 1855) are preserved in 

 the Academy of Natural Sciences of Philadelphia : A. troglodytes, A. spicn/lj'i ,-, 

 A.fossf/rum, A. angustatiis, A. laiimanus, and A. (ulmict. The Museum of Com- 

 parative Zoology also possesses types of A. troglodytes, A. spiculifer, A.fossn- 

 rum, A. laiimanus, and A. advena. A. fossarum is not separable from A. troglo- 

 ////les. Le Conte's A. nutiiieidatns remains yet unknown. (See p. 29.) 



The Tim Forms of the Mules. 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 the 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.! 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 opportunity as yet to examine their microscopic structure. 



India// '/(ins of Hcrmaplirodilimi in Camhirii*. Perhaps the only recorded 

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

 lobster (IIiniKinis t>til</<tris) described and figured by F. Nicholls in 1730. In 



: Pages .'1, -n. 



i Ou the Sn.r.-illod Dimorphism in the Genus Cambarus, by Walter Faxon. Amcr. Jour. Sci., Vol. 

 \\\ II. |>p. k'-H, January, 1884. 



J Ser I la-en's Plate II. 



; An \ccniiut of the llrrmaphrodilie Lobster presented to the Royal Society by Mr. Fisher, examined 

 and dissected, by F. NicUk Phil,,*,,,,!,. Trans. Roy. Soe. London, Vol. XXXVI. 'NO. -113, p. 290, 1730 

 ( Abridgment, Vol. VII. Pt, III. ,,. \->\, PI. IV., 17:SJ). l',i- a S rm-ral account of limnaphrodilir. and other 

 anomalous conditions among Ilic (YuMaiva, set Fa\on, On Some Crustacean Deformities, Bull Mus Comp. 



. \,,| vill. No. 13, 1881 



