376 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



exposed at low tide. Alpheus vilnus has a similar environment and is similarly colored. Alpheus 

 heterochelis from Nassau, New Providence, on the other hand, lives under loose stones, amid the 

 white coral sands of the beach, and is noticeably transparent, looking as if the color had been 

 ble<ached out of it. The body is sprinkled with dots of brown pigment. The claws and legs are 

 pale greenish. Young and old are invariably colored alike. 



In a collection of adult Alpheus of either sex of the same or of several species, where there is 

 a difference in size of the large claws, it is noticed that either the right or the left, indifferently, 

 may be the greater. As we will see, this differentiation of the chehe begins in one instance before 

 the animal is hatched. Is this right and left handed condition to be explained by inheritance 

 from the parents ? In about forty larvai of a small brood of Alpheun saulcyi, all invariably had the 

 left claw eidargcd, and in a smaller number (all that were preserved), from another female of the 

 same species, the left chela was also in each case the larger. This would indicate that the young 

 of the same mother have always the same claw, either right or left, the greater, and that this phe- 

 nomenon is one of direct heredity from the parents. But to prove this it is only necessary to trace 

 right and left handed broods to parents which are themselves right and left handed, respectively. 

 This, unfortunately, I have not done, as my attention was not called to the subject while at the 

 seashore.* 



The breeding season of Alphens begins at Beaufort, N. C, about April 1. It covered the 

 period of our staj- at Nassau (March to July), and ])robal>ly Ix^gau earlier and lasted considerably 

 later.! There the temx^erature is high and remarkably constant, the annual range being about 15° 

 (temperature of air 70° F. in March, 80° in June), and in conseuuence the early phases of devel- 

 opment are rapidly passed. Not one prawn in a hundred was found with eggs in an earlier stage 

 than that of yolk segmentation. 



II. — VARIATIONS IN ALPHEUS HETEROCHELIS. 



A renewed comparison of AlpheuK heterochdis with the Nassau form lends support to the con- 

 clusion already reached that we here have to do with two varieties of the same species. There are 

 certain diflerences, which systematic zoologists might regard as of specific value, but they are no 

 greater than we have proved to exist among individuals of the same si>ecies living in the same 

 sponge, (v. Section V.) 



The Nassau specimens average smaller, but the chief ditlerence lies in the shape of the small 

 chela. The propodus of this appendage in the Nassau form is relatively shorter and thicker in 

 both sexes. Both tiugers are nearly cylindrical, and covered with hairs, which are distributed 

 either singly or in tufts. In the Beaufort heterochelis there is a striking variation in the small 

 chela which appears to have escaped detection. Judging from the small collection at my command 

 it is a .sexual variation. In the females the small chela is like tliat of the Nassau form, but is 

 usually longer and .slenderer. The dactyle is about one-half the length of the propodus. In 

 the males the dactyle is relatively much shorter, and has a median longitudinal carina which is 

 continued into the apex of the claw. In transverse section the dactyle is trihedral, with two con- 

 cave sides, corresponding to the deep groove on either side of the keel. These grooves are fringed 

 with a row of stout plumose .setie. Similar rows of set;e occur on the sides of the o[)posing 

 " thumb." 



Perhaps the most interesting variation wliich I have observed in the Beaufort heterochelis has 

 reference to the size of the egg. The eggs in this locality have an average diameter ot about one 



" Mr. J. J. Northrop, of Coliiinbia College, while at Nassau iu the winter and sprinj; of 1890, kindly oflered to 

 collect for me some specimens o( Alpheus saiihyi with young. Ou February 10 be coIbMited six females, five from greeu 

 sponges, one of which h.a(l a brood of sixteen young, and one sratill female with three larv.-e from the " loggerhead" 

 sponge. In the first instance the left chela w.as the largest in the mother anA iu each of the sixteen young. In the 

 latter, two h,ad the right claw enlarged and one the left. The inference is snggested that when the claw of the same 

 side is iuvariaWy the greater in all the young, this character is doubly inherited from both father and mother, but the 

 data are insulficient to settle this point. 



t Professor H. V. Wilson found this species breeding around Greeu Turtle Key from July until December. Mr. 

 Northrop found newly hatched you ug early in February. It therefore breeds the year through, which is probably 

 true of many of the Crustacea. 



