October 7, 1898.] 



SCIENCE. 



481 



through the glass. Shut one eye so as to get 

 rid of binocular perspective. 



You can now at will change the relative 

 position of the two parts of the rim. At one 

 moment you see the farther rim through the 

 glass in its true position ; at another it seems 

 the nearer of the two and you seem to be look- 

 ing into the mouth of the goblet. 



Now, if the glass were rotating, it is evident 

 that it would seem to rotate in the one direc- 

 tion or the other, according as we imagined 

 the real or the reversed position of the rims. 



The phenomena can be seen with both eyes 

 open, but is clearer with one eye shut for the 

 reason already given. 



Now, I think the phenomenon of the rotating 

 fan is explained in a similar way. The ob- 

 server, I suppose, looked at the fan from a little 

 below the horizontal, but seemed to be looking 

 at it from above, when the rotation was ap- 

 parently reversed. ^^^^^^ LeConte. 



Berkeley, Cal., September 24, 1898. 



[A similar explanation has been sent us by 

 Mr. Garrett P. Serviss, Jr. It is the explana- 

 tion of Sinsteden, who first described the phe- 

 nomenon in 1860, as stated above by Mr. Pierce. 

 Cf. von Helmholtz, Physiol. Optik., 1895, p. 

 770.— Ed. Science.] 



SCIENTIFIC LITERATURE. 

 Memoirs from the Biological Laboratory of the Johns 

 Hopkins University, IV., 1. The Cubomedusse. 

 A Dissertation presented for the Degree of 

 Doctor of Philosophy, in the Johns Hopkins 

 University, 1897. By Franklin Story Co- 

 NANT. A Memorial Volume. Baltimore. 

 1898. 



The late Dr. Conant, it will be recalled by 

 many, was a member of the marine laboratory 

 of the Johns Hopkins University, stationed dur- 

 ing the summer of 1897 at Port Antonio, Ja- 

 maica. Toward the end of the season's work 

 fever broke out. The director of the expedi- 

 tion. Dr. J. E. Humphrey, died in a sudden and 

 alarming manner. Dr. Conant assumed charge 

 of the laboratory, and, though aware of his own 

 great danger, remained in Port Antonio, de- 

 voting himself to the service of others who 

 needed his help. This generous subordination 



of self cost him his life, for he contracted the 

 fever, and, though able to reach this country, he 

 died a few days after his arrival in Boston. 



Dr. Conant' s many friends, well aware of his 

 candid, judicial mind, his keenness and persis- 

 tency in observing and in reasoning from ob- 

 servations to a conclusion, have entertained the 

 highest expectations of the work he was to do 

 in science. Cut off at the beginning of his ca- 

 reer, he leaves behind him several smaller pa- 

 pers and the dissertation before us. On closing 

 this volume the author's friends will feel con- 

 firmed in their high opinion of his abilities, and 

 those who did not know Dr. Conant will rea- 

 lize with regret that an able and conscientious 

 naturalist has been removed from our midst. 



Dr. Conant' s dissertation, published as a me- 

 morial volume by his friends, fellow students 

 and instructors, with the aid of the university 

 in which he had recently taken his doctor's de- 

 gree, deals with the anatomy and classification 

 of one of the most interesting groups of jelly- 

 fish, the Cubomedusse. In this group, embrac- 

 ing but a small number of species, the scypho- 

 medusan structure, with which most of us are 

 chiefly familiar through the study of Aurelia, 

 Oyanea or Dactylometra, is in general presented 

 as destitute of the complications which charac- 

 terize the more common forms. This simpli- 

 city in general structure places the group close 

 to the stem-forms, Tessera and Lucernaria, them 

 selves scarcely more than sexually ripe Scyphis- 

 tomas, and makes a comparison with existing 

 Actinozoa an easy matter. Curiously enough, 

 the members of this primitive group possess the 

 most highly developed sense-organs as yet de- 

 scribed among coelenterates, the nervous sys- 

 tem being correspondingly differentiated. In 

 one other respect the Cubomedusae are unique, 

 in that they alone among the Scyphomedusse 

 possess a velum. The phylogenetic origin of 

 this velum (velarium) has been the subject of 

 some discussion, the balance of opinion inclining 

 to the belief that it has arisen through the fu- 

 sion of marginal lobes similar to those found in 

 the Peromedusae and the Ephyropsidse (Nausi- 

 iAoe),and is merely analogous to, not homologous 

 with, the velum of the Hydromedusse. That 

 this is the case is borne out by the presence in 

 the velum of gastrovascular diverticula. This 



