58 Papers from the Marine Biological Laboratory at Tortugas. 



it and the asymmetry is reversed, as first shown by Przibram. It is 

 not known on which side the large claw develops first. I interpret Her- 

 rick's records as demonstrating that the large claw develops first on the 

 left side in Synalpheus minus (Alpheus saulcyi). 1 It was found in my 

 specimens about as frequently on the right as left side in both large 

 and small individuals. Of 50 taken at random, 22 had the large claw 

 on the left and 28 on the right. In another species Przibram found 40 

 individuals with the large claw on the left and 47 on the right. 



The Pontoniid Typton tortuga, as was stated above, has the pincer- 

 like appendages of the fifth thoracic segment well developed. One of 

 these claws is much larger than the other, but the asymmetry is not as 

 great as in the Alpheids. Both of these claws are snapped with a sharp, 

 clicking sound. When the large claw is removed the small one grows to 

 take its place, as in the Alpheids. 



The two animals do not perhaps resemble one another as much in 

 general coloration as in general form, though the color varies so much in 

 both animals that these differences are not at first noticeable. The color 

 darkens with age. The Alpheid varies from the color shown in plate i, 

 fig. i, to a light brown. Specimens with a claw like fig. 2 may be a dull 

 cream or light brown in general color. The nerve cord and some other 

 organs may be surrounded by red pigment cells. Yellowish, brownish, 

 or reddish glands in thorax or abdomen may show through. 



The Pontoniid Typton tortugce varies from the color shown in fig. 3 

 to an almost colorless condition, or to a light red or a pale bluish. The 

 large claw of the pale specimens is often paler than the small claw in 

 fig. 3. After the large claw has been removed the small one grows to 

 take its place, but for some time retains more or less its general form and 

 color. Often yellow, brown, or green glands show through in the thorax 

 and abdomen. 



As these animals pass their entire adult existence in the dark or 

 dim light, it is improbable that their color is of much significance in their 

 struggle for existence; hence it would not be fixed by natural selection. 

 The fact that their eyes are not degenerate might indicate that they 

 sometimes come near the mouths of the passages in the sponge. Per- 

 haps they are forced out when the sponge becomes overcrowded, but 

 I doubt that many of the larger ones would find another sponge before 

 they were eaten by fish. Neither form was found in any other habitat, 

 though Herrick records the Alpheid from reef rocks as well as loggerhead 

 sponges in the Bahamas. 



The Alpheid has large eggs, few in number, attached to the swim- 

 merets of the female. The metamorphosis is abbreviated, and in some 

 cases omitted. The young remain attached for a time to the mother, 

 but perhaps always leave the sponge and live a short pelagic life before 

 finding another sponge. The female Pontoniid deposits numerous small 

 eggs on the swimmerets. These hatch into small larvae which lead a 

 comparatively long pelagic life before acquiring the form and habits 

 of the adult. 



1 Brooks and Herrick: The Embryology and Metamorphosis of the Macroura. 

 Mem. Nat'l Acad. Sci., 5, 1891. 



