of this kind, showing that it reacts to different 

 backgrounds under varying light conditions. 



Hess (1940, 1941) demonstrated that A. arrnilla- 

 tux is sensitive to light in many regions of the 

 body, regardless of the amount of time elapsed 

 since the preceding molt. At Tortugas, he found 

 that diurnal molting in this shrimp is apparently 

 controlled by daily temperature changes, molting 

 occurring when the temperature rises to or above 

 29° C. Animals in constant temperature failed to 

 exhibit diurnal molting as did ovigerous females. 



Darby (1934) studied regeneration of chelae 

 in A. armillatus and Synalpheus longicarpus to- 

 gether with determination of right or left handed- 

 ness. He found that in development of chelae a 

 stage was reached that permitted determination 

 of which side would have a large chela. Equal 

 chelae were produced experimentally and were 

 of three varieties: (1) both small (pinch claws) ; 

 (2) both large (snap claws) ; and (3) both 

 intermediate. 



Darby offered an hypothesis, involving two 

 substances and a metabolic condition, which could 

 explain the regenerative phenomena in these and 

 allied crustaceans. In such animals, a substance A 

 is produced which controls production of pinch 

 claws ; but at certain stages in the intermolt cycle 

 a substance B is produced, for a limited time, and 

 is concentrated in whichever claw is regenerating 

 or already modified as a snap claw. This circum- 

 stance will produce or reinforce production of a 

 snap claw. Chance alone is responsible for whether 

 a snap claw will be on one side or the other, or 

 whether the animal will be symmetrical. Also, 

 time at which regeneration occurs depends on 

 chance. 



Genus Synalpheus Bate, 1888 



Banner, 1953, p. 26.— Hemming, 195Sb, p. 161. 



KEY TO SPECIES IN THE CAROLINAS 



a. Dactyls of third, fourth, and fifth legs with two very 

 unequal hooks, ventral strongest (broadest) ; an incon- 

 spicuous, obtuse supernumerary process proximal to 



ventral hook fritzmuelleri subsp. (p. 69). 



aa. Dactyls of third to fifth legs with two hooks approxi- 

 mately equal in width at base. 



b. Dactyls long and slender, hooks continuing general 

 direction of axis of dactyl : stylocerite longer than 

 basal article of antennular peduncle : lamella of an- 

 tennal scale present. 



c. Frontal teelth more or less equilaterally tri- 

 angular, at times with concave margins, but 

 never with an inferior vertical prolongation to 

 rostrum ; basicerite strongly spinous above 



minus ( p. 70). 



cc. Frontal teeth always longer than wide, spinous ; 



rostrum armed with a ventral prolongation which 



embraces ocellary beak ; basicerite unarmed 



above townsendi (p. 72). 



bb. Dactyls short, hooks strongly curved, ventral one 

 usually bent at considerable angle to axis of dactyl ; 

 stylocerite not exceeding first article of antennular 

 peduncle ; antennal scale lacking lamella in male, 

 small in female longicarpus (p. 73). 



Synalpheus fritzmuelleri Coutiere 



Figure 56 



Synalpheus fritzmuelleri Coutiere, 1909, p. 35, fig. 18. — Ver- 

 rill, 1922, p. 97. Schmitt, 1935a, p. 14S. 



Recognition characters. — Rostrum slender, 

 compressed, acute from dorsal view, a little longer 

 than orbital spines, reaching to midlength of 

 visible portion of basal antennular article. Orbital 

 spines wide at base, acuminate; margins incurved. 

 Eyes completely covered by carapace. Antennular 

 peduncle with stylocerite of basal article reaching 



Figure 56. — A, Synalpheus fritznwelleri Coutiere, anterior 

 portion of animal in dorsal view ; B, Synalpheus fritz- 

 muelleri elongatus Coutiere, anterior portion of animal 

 in dorsal view ; 1 mm. indicated. 



MARINE DECAPOD CRUSTACEANS OF THE CAROLINAS 

 763-049 O — 65 6 



69 



