Makch 27, 1908] 



SCIENCE 



491 



cies may act together, the first, however, 

 slightly dominating the second. By means 

 of these tendencies the young turtles find 

 the water. (2) After twelve hours at the 

 outside, their phototropism is lost. (3) 

 Swimming and floating are congenital in- 

 stincts, but diving is a process which must 

 be learned. (4) After entering the water, 

 there is a definite period of ' ' getting out to 

 sea," as it were, followed by a definite 

 period of rest. (5) The edibility of each 

 object encountered is tested, i. e., there is 

 no instinctive selection of a particular food. 



The Experimental Control of Asymmetry 

 at Different Stages in the Development 

 of the Lobster: V. E. Emmel, Harvard 

 Medical School. 



A series of experiments were made at the 

 following stages in the development of the 

 lobster: (1) the second larval stage, (2) 

 the fourth stage, (3) fifth stage, (4) 

 twelfth stage or year-old lobsters. All of 

 these experiments attempt to determine to 

 what extent asymmetrical differentiation of 

 the chelse can be controlled by the amputa- 

 tion of one chela, thus giving the re- 

 maining chela the greater opportunity for 

 growth. 



The results of these various experiments 

 support the following conclusions : 



1. That in the first four larval stages of 

 the lobster, the development of right or 

 left asymmetry can be controlled by the 

 amputation of one of the chelffi. 



2. During the fifth stage the controlling 

 influence of such amputations disappears. 



3. In later stages when the asymmetry 

 of the chelae has become normally estab- 

 lished, the amputation of neither one nor 

 both chelae will produce a reversal of asym- 

 metry. 



4. And finally, since up to the fifth stage 

 either right or left asymmetry of the chelae 

 can be produced at the will of the experi- 

 menter, this asymmetry does not appear, 



therefore, to be directly predetermined or 

 inlierited, but may be controlled by factors 

 arising in the course of development. 

 What these factors are, has not been de- 

 termined, but the present results do not 

 indicate that they are "an inverse organ- 

 ization" of the egg, or an "alteration in 

 the localization of germinal substances." 



The Specific Gravity of the Constituent 

 Parts of the Egg of Chcetopterus and 

 the Effect of Centrifuging on the Polar- 

 ity of the Egg: P. E. Lillib, University 

 of Chicago. (To be published in the 

 Proceedings of the Central Branch.) 



Instance of a New Species of Crustacean, 



apparently in Process of Evolution: 



Addison E. Vereill, Yale University. 



An account was given of a peculiar race 



of the gi*apsoid genus, Sesanna, studied in 



Bermuda, in 1901. The common species in 



Bermuda {S. Bicordi) lives ordinarily at 



and just above high-tide level, within easy 



reach of water. It is often seen running 



actively about among the stones and dead 



seaweeds. It may almost always be found 



under masses of Sargassum cast up on the 



shores, as well as under stones. 



The new form seems to be a subspecies 

 of a variety of S. Bicordi, which may be 

 actually in process of development into a 

 genuine species, by natural selection and 

 physiological isolation. 



It was found living under stones in dry 

 upland fields and nearly barren waste 

 lands with thin soil, where the scanty vege- 

 tation consisted of wiry grasses and 

 dwarfed shrubs and weeds. It was asso- 

 ciated with a few species of ants, beetles, 

 cockroaches, spiders, land-shells, etc. When 

 the stones were turned over it usually ran 

 away very actively and sought shelter 

 under other stones, but did not seek the 

 water, as most species do. Its general ap- 

 pearance was very unlike S. Bicordi. 

 The carapace appears more rough and 



