374 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



In Alpliem heterochelis the dactyle of tlie large pincers is a curved blade which shuts down 

 into a groove on the occludent 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 corresponding 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 produced 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 1 have freqncnth -seen specimens of A. licterochelix, 

 when prepared for combat, facing each other for several seconds with claws distended to the 

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

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

 that I have seen individuals killed and almost cut in two by a single blow. \V. K. E.) 



A large brown sponge, Hi win in in-cut a, which is not to he mistaken, grows on the shallow 

 reefs and off the. shores of all the Bahama Islands which I 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 1A feet in 

 diameter. There is commonly one, sometimes two, large e.xhalent chimneys into which small tish, 

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

 ithas 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 specie.^ of Alphens, 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 specimen. 



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

 the large chehe, 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 difficulty, 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. These are most commonly 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 inspection the body is seen to be sprinkled with cells of reddish and yellow pigment. 



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

 water. There are several varieties of 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 pour 

 out when broken open. In about nine out often of these sponges one will find 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 are distinguished by their large size (averaging about L'.' 1 .' in length) and uniform color. 



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

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



The female is practically inert during tlie breeding season, and at. such times is well protected 

 in her sponge or against any green surface by the bright green ovaries which fill the 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 pigment ou the claws was more orange 

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

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



