Febbuaey 13, 1903.] 



SCIENCE. 



245 



it is small and fau-shaped, containing 

 about 500 eggs. 



The ends of the oviducts in the copula- 

 tion of M. pilata become firmly united, 

 so that the animals may be pulled about 

 with considerable freedom. While in cop- 

 ulation the swollen ends of the oviducts 

 are spherical in form and the color is in- 

 tensified. It may take three hoiirs for the 

 distended oviduct to become completely 

 retracted. The egg mass is laid in the 

 form of a straight or undulating string 

 frequently six inches long. There are 

 from two to eight eggs in a single section 

 of the string. Deposition occurs from 

 twelve to twenty-four hours after copula- 

 tion. 



The spawn of Doris is long and rib- 

 bon-lUce, one fourth of an inch wide. The 

 eggs are arranged in regular rows at right 

 angles to the long axis of the spawn mass. 



j3Eolis papulosa lays about forty sep- 

 arate, oval, salmon-colored egg masses, all 

 of which are united into one large, gelat- 

 inous mass. 



Death-feigning in Sand Fleas: S. J. 



Holmes, -Ann Arbor, Mich. 



Death-feigning in the large sand-flea, 

 Talorchesiia longicornis, is a pronounced 

 instinct. This species is nocturnal in its 

 habits, and during the day lies curled up 

 in its burrows in the sand in a condition 

 apparently much like the sleep of higher 

 animals. When dug out of its burrows, 

 Talorchesiia may remain curled up and 

 motionless, or it may assiune such a con- 

 dition after a few hops in the sand. In 

 assuming the death-feigning attitude, Tal- 

 orchesiia flexes its body, draws up its legs, 

 and bends its antennae under the thorax. 

 It will then remain motionless, often for 

 a long time, and may usually be picked 

 up without betraying any evidence of ani- 

 mation. The utility of such an instinct 

 is obvious, as it enables its possessor to 



escape detection. By lying quiet in the 

 sand, which it closely resembles in color, 

 Talorchesiia would easily be overlooked by 

 predatory birds and mammals, whereas if 

 it endeavored to escape by hopping away, 

 its large size would render it an easy 

 victim. 



The terrestrial amphipods form a group 

 which has only recently adopted the habit 

 of living upon land. The instinct of 

 death-feigning is, therefore, one of recent 

 origin, as it is one which has doubtless 

 been acquired in adaptation to the habit 

 of living above water on sandy beaches. 

 We naturally look to the behavior of the 

 aquatic relatives of this species and of 

 other terrestrial forms for light upon the 

 origin of this instinct. Two other species 

 found on the New England coast, Orchestia 

 palusiris and 0. agilis, fortunately exhibit 

 intermediate modes of behavior which con- 

 nect the death-feigning instinct of Talor- 

 chesiia with the so-called thigmotactic re- 

 actions of the aquatic amphipods. Nearly 

 all the littoral species of aquatic amphi- 

 poda manifest a strong pi-opensity to keep 

 in contact with solid objects. When free 

 from contact they are restless. They usu- 

 ally endeavor to insinuate themselves be- 

 tween objects, so as to secure a maximum 

 of contact; then they ^ie quiet, usually 

 with the antennae bent back and the body 

 flexed. 



The behavior of the two species of 

 Orchesiia studied shows that they possess 

 certain fundamental features of conduct 

 in common, and that the death-feigning 

 of Talorchesiia is nothing but an exag- 

 geration and specialization of the thigmo- 

 tactic proclivity which these forms share 

 with the aquatic amphipoda. 



Variation and Natural Selection in Lepi- 

 doptera: H. E. Crampton, Columbia 

 University. 

 The relation between the process of 



