REGENERATION IN CAMBARUS. 299 



A discussion of the results obtained by Morgan and Miss 

 Steele will be found in connection with the discussion of my own 

 observations in a later portion of this paper. 



ABNORMAL SWIMMERETS. 



Anomalous variations not of congenital origin are of little in- 

 terest to the student of evolution ; for it has never been definitely 

 demonstrated that any acquired somatic variation is inherited. 

 Moreover, no very important laws of variation are likely to be 

 discovered by a study of teratological specimens. Nevertheless, 

 it is advisable to place interesting cases of abnormal growth and 

 regeneration on record, for we may finally acquire a knowledge 

 of the physiology and mechanics of development sufficient at 

 least to explain the origin of such anomalous variations. 



The swimmeret shown in Fig. I is the right appendage of the 

 second abdominal somite of a female C. I'irilis. The pleuron is 

 much deformed, as is readily seen if compared with the normal 

 pleuron of the opposite side of the same somite. The coxopo- 

 dite of the abnormal appendage is much larger than normal. 

 From this enlarged basal piece arise two appendages, one of 

 which, near the posterior side of the coxopod, seems on casual 

 observation to be a beautiful case of duplicity. The parts are 

 perfectly doubled from the proximal portion of the basipodite 

 outward. The two pleiopods thus united are normal in every 

 particular beyond the point of union, the posterior member being 

 somewhat larger than the anterior. From the anterior portion 

 of the large coxopodite, completely separated in point of origin 

 from the double pleiopod, arises another appendage which is 

 uniramous, but of a size and structure typical of the endopodite 

 of the second pleiopod. 



It is an interesting circumstance that the first pleiopod lying 

 immediately anterior to the one just described is also abnormal. 

 This swimmeret is shown in Fig. 2. The lower portion of the 

 appendage is much enlarged, and at the proximal end of the 

 basipodite, there is a posterior projection set with stiff hairs, 

 reminding one somewhat of the structure of the coxopodite of 

 the pereiopods. 



The third abnormal swimmeret is from a male C, virilis which 



