14 A REVISION OF THE ASTACIDA. 
curiously modified so as to resemble the same parts in the males of the 
genus Astacus. The transverse suture near the base of the appendage is 
obliterated ; the apical half, instead of being membranous and frmged with 
sete, as in the normal female, is firm and naked, and rolled from the out- 
side inward so as to form on the inner side a groove which is converted into 
a tube just at the tip, owing to the closeness of the coil at that point. The 
whole organ is larger and thicker than in the ordinary female, although not 
so large as in the male. The tip is altogether destitute of the recurved hooks 
of the normal male organ in this species. 
The fourth specimen belongs to C. propmquus Girard. It is 72 milli- 
meters long (M. C. Z., No. 3432). It agrees with the female in every respect 
except the shape of the first pair of abdominal limbs, which are partly trans- 
formed into the condition which obtains in the male. The modification of 
the appendages has not gone so far on the right side as on the left. In both, 
the transverse suture is obliterated ; the basal half is thick and corneous, 
and produced into a prominent tubercle on the inner side, as in the male. 
The apical half of the right appendage retains the membranaceous and 
setiferous character of the female appendage, while in the left it is more 
corneous, and rolled from without inwards in such a fashion as to form an 
inner and an outer part somewhat as in the male, though neither part is 
in this case produced into an acute style, as in the normal male, and the 
outer part retains the membranaceous setiferous tip. 
These specimens are in such a: bad state of preservation that a deter- 
mination of the sex from the internal generative organs in several of 
them is wellnigh impossible. Dissection of the first-described specimen, 
with the orifices of the generative organs in the base of the last pair of legs, 
as in the male, revealed many large ovarian eggs, and I little doubt that 
the other three individuals are females which have assumed some of the 
characters of the opposite sex.* It would be interesting to determine from 
fresh specimens whether such monstrous conditions as those just described 
ever denote true hermaphrodites, producing both male and female genera- 
tive elements, or whether they may involve sterility. They are the more 
interesting from the fact that hermaphroditism exists as a normal condition 
in another highly specialized order of Crustacea, the Isopoda.t 
* Boas (Vidensk. Selsk. Skr. 6te Raekke, naturvidensk. og Math. Afd., Bd. I. pp. 94, 184) says he has 
seen a female Thalassina anomala and a female Astacus fluviatilis with abdominal appendages like the male, 
but gives no particulars concerning these specimens. 
+ See Bullar, Journ. Anat. Physiol., Vol. XT. p. 118, 1876; Ann. Mag. Nat. Hist., 4th Ser., Vol. XIX. 
p. 254, 1877; and P. Mayer, Mitth. Zoolog. Station zu Neapel, Vol. I. pp. 165, 177, 1878. 
