MICHIGAN ACADEMY OF SCIENCE. 67 



day by dealers, Miiile thousands of lobsters may be examined without 

 meeting a single case of repetition or duplication of parts," 



Most of Bateson's^ variations described for Trnstacea relate to chelae; 

 only one is of a chelate ambulatory leg, two of antennae, and four of non- 

 chelate ambulatory legs. He thinks that there is no ground to suppose 

 that this doubling "is the result of injury or regeneration after injury.'^ 

 When the limb of a crab or lobster is injured, it is usually thrown otf 

 bodily, while the extrai parts most often spring from the periphery of 

 the chela. But since, according to Heineken, such mutilated parts are 

 sometimes retained, this must not be insisted upon.'' 



The second abnormality, Fig 2, was found in a specimen of Camharus 

 hlandingl aciitus (Girard). This crayfish possessed female characters^ 

 except for the fact that the first left abdominal appendage was exactly 

 like that of a male in form, though its size was smaller than that of 

 a normal male. The most careful dissection showed no sign of testes 

 or male genital ducts, though the ovary was somewhat shrunken on the 

 left side. The specimen had stood in alcohol for at least three months, 

 however, and the shrunken condition may have been due to this cause. 



Numerous examples of hermaphrodite crayfish have been reported. 

 These are mostly females with some male organs. The most striking 

 instance is that given by Hay- in which both male and female interual 

 organs were present. I know of no published record, in this species of 

 crayfish, at least, corresponding exactly to what I have described. 



As to the cause of hermaphroditism Hay remarks, "It would there- 

 fore appear that in the genus Cambarus, at least, hermaphroditic indi- 

 viduals are females which, owing to some ambiguity of the formative 

 cells in the embryo, have developed to a greater or less degree the 

 characters of the opjiosite sex." 



Andrews^ is somewhat more specific on this subject: "^letm while the 

 totality of facts known seems to mean that the gynandromorph cray- 

 fishes are caused by unknown disturbances, which may happen at 

 various periods of ontogeny, though probably more often in the ovariao 

 egg; that these disturbances may have no connection with the gonads; 

 and that if in some cases the disturbances are possibly associated with 

 polyspermj^ in general they seem more fundamental and deep seated 

 amidst the causes of symmetrical form within the egg." 



I have presented these abnormalities and some opinions of others who 

 have worked upon the subject, making no attempt to say who is on the 

 right track. Certainly the Avhole subject is open to much more investi- 

 gation before it shall be settled. 



Univ. of Michigan, April 12, 1910. 



iBateson, Wui., "94. Materials for the Study of Variation, p. 526. 



=Hay, William Perry, :05. Instances of Hermaphroditism in Crayfishes. Smithsoniaa 

 Miscellaneous Collections, Vol. 48, Part 2. pp. 222-228. 



^Andrews, E. A.. :09. A Male Crayfish with Some Female Organs. The American 

 Naturalist, Vol. XLIII, Xo. 512, pp. 401-472. 



