374 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



In AlplienH heterochelis the dactyle of the large pincers is a curred blade which shuts down 

 into a groove on the occludeiit margin of the " thumb," and closes over the latter like a pair of 

 shears. The huge stopper like tooth is borne on the inner and proximal edge of the dactylopodite 

 and fits neatly into a corre.s])onding pit in the " thumb," in line with the groove just mentioned. 

 The object of this plug is evidently to steady the movable dactyle and to prevent lateral strain 

 and the dislocation which might result, and thus to give it a strong grip on any object which it 

 has seized. In alcoholic specimens in which the relations of the parts are well preserved the stop- 

 per works freely in and out the well, and not like a " tightly packed piston from a cylinder closed 

 at one end." 



(The claw is widely opened, before the sound is produced, but the sound is not prodnced while 

 the claw is open, but at the instant when it is violently and suddenly closed. It is due to the 

 impact of the "thumb" and "finger," and I have frequently seen specimens of A. heterochelis, 

 when i)repared for combat, facing each other for several seconds with claws distended to the 

 utmost. In these cases the " snap" does not come until the claw is closed. In fighting the 

 claw is not used as a clasper, but as a saber. The sharp external edge is a weapon of such eflQciency 

 that I have seen individuals killed and almost cut in two by a single blow. — W. K. B.) 



A large brown sponge, Hircinia arcuta, which is not to be mistaken, grows on the shallow 

 reefs and off the shores of all the Bahama Islands which 1 visited. It is found from just below 

 low tide mark out to one-half a fathom or more of water, where its great size and sooty brown color 

 distinguish it at once on the white bottom. These "loggerheads "are round and much flattened (the 

 smaller ones more vase-shaped), and of a coriaceous texture; they sometimes measure li feet in 

 diameter. There is commonly one, sometimes two, large exhalent chimneys into which small fish, 

 young spring lobsters, and other Crustacea, often beat a hasty retreat. It is easily broken open since 

 it has no consistent skeleton. If a sponge colony of this kind is pulled and torn apart, one is certain 

 to find it swarming and crackling with a small species of Alpheus, which quarter themselves in 

 the intricately winding pores of the sponge. The sounds emitted from every fragment of these 

 mutilated sponges remind one forcibly of " those made when sparks are taken by the nuckles from 

 the prime conductor of a small electrical machine," as Wood-Mason remarks. Hundreds of indi- 

 viduals may be collected from a single large si)ecimen. 



These animals have an average length of about 12™'". They are nearly colorless, excepting 

 the large cheliiB, which are tipped with brown, reddish orange, or bright blue. The females are so 

 swollen with their eggs or burdened with the weight of those attached to the abdomen that they 

 can crawl only with great difiBculty, if taken from the water. The eggs are few in number and of 

 unusually large size, their diameter varying from one-twenty-second inch to one-twenty fifth inch, 

 and their number from six to twenty. Tiiese are most conimonly yellow, but may be either bright 

 green, olive, greenish white, brown, brownish yellow, or dull white. The ova and ovarian eggs 

 have always the same tint in the same individual. Although translucent and apparently colorless, 

 upon close inspecition the body is seen to be sprinkled with cells of reddish and yellow pigment. 



Anotlier quite different sponge grows on all the reefs in from one to two fnthoms or more of 

 water. There are se%'eral varieties ot this, which may be told by their olive green color, yellow 

 flesh, and clumpy, irregular shape, as well as by the putrescent mucous which some of them ponr 

 out when broken open. In about nine out often of these sponges one will fiinl a single pair of 

 Alpheus (rarely more than this), which resemble those living in the brown sponge, but differ from 

 them in several important points. We are concerned at the present with the color variations only. 

 They iire distinguished by their large size (averaging about 23""" in h-iigth) and uniform color. 

 The females exceed the males greatly in l»ulk, owing to the large size and number of their eggs. 

 In both sexes the hirge claws are bright red (v. PI. iv, and for details section iv). 



The female is practically inert during the breeding season, and at such times is well juotected 

 in her sponge or against any green surface by the bright green ovaries which fill tlie whole upper 

 part of the body and by the mass of similarly colored eggs attached to the abdomen below. Only 

 two pairs, or four individuals, out of a hundred or more which were examined showed any variation 

 from these colors. In these the eggs were yellow, and the i)igment on the claws was more orange 

 than red. The table which follows shows the variations between two large females taken, respec- 

 tively, from the brown and green sponges, and between the size, number, and color of the eggs. 



