MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



3B8 



shown in Fig. 1. The following notes on the variations in the coloration and habits in Alplieus, 

 particularly in .4. saulcyi, are taken from a paper by Mr. Ilerrick published in the Johns Hopkins 

 University circulars. 



VARIATIONS IN THE HABITS AND COLORATION OF ALPHETJS. 



Some of the species of Alpheus are usually or even universally found living as parasites within 

 the water tubes of sponges, and it is extremely interesting to find that individuals of the same 

 species, living in ditferent species of sponges, may themselves ditier greatly in color and in habits. 



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

 reefs and off the shores of many if not all the Bahama Islands. This is called the " loggerhead 

 sponge" by the fishermen, and 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 onco on the 

 white bottom. If a sponge colony of this kind be pulled and torn apart, one is certain to find it 

 swarming with a small species of Alpheits, which quarter themselves in the intricately winding 

 pores of the sponge. Hundreds, or even thousands of individuals might be collected from a single 

 large specimen. These animals vary from one-eighth to three-fourths of an inch in l«iigth. 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 to 

 one twenty-fifth of an inch, and their number from six to twenty. These are most commonly yellow, 

 but may be either bright green, olive, flesh color, brown, or dull white. 



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 mucus which some of them pour 

 out when broken oj)en. In nearly nine out of ten of these sponges one will find a single pair of 

 Alphei which resemble those living in the brown sponge in most particulars, although they differ from 

 them in several important points. They are distinguished by their large size, and by their peculiar 

 and very uniform color. They vary in length from two-thirds to one and two-thirds inches. The 

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



Both sexes are nearly transparent and colorless excepting the large claws, which are bright 

 vermilion-orange ( PI. iv). The female is practically inert during the breeding season (which lasted 

 during our stay, March to July), 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 similary colored eggs attached to the abdomen below. Only two pairs, or four individuals, 

 out of a hundred or more which were examided showed any variation from these colors. In these 

 the eggs were yellow, and the pigment on the claws more orange than red. The table which fol- 

 lows shows the variations between two large females taken respectively from the brown and green 

 sponges, and between the size, number, and color of the eggs. 



These two forms, apparently distinct, are seen however, by closer examination, to belong 

 to the same species, although they show very interesting variations. The Alpheus living in the 

 brown sponges tends to vary in several ways, chiefly in size and in the color of the body and eggs. 

 The rostrum usually has three spines, but occasionally only two are present, the median one being 

 lost. It is evident that these animals are perfectly protected from outside enemies while within 

 the torfuous mases of the sponge, as their numbers would show. Parasites such as Isopods, how- 



