272 



THE POPULAR SCIENCE MONTHLY. 



" The various attacks on the theory of de- 

 scent," says President Jordan, " have nearly 

 all centered on the question of the origin of 

 man." But these attacks are wholly un- 

 reasonable. " Our objections to recognizing 

 our kinship with the lower forms — if we 

 have any such objections — rest on reasons 

 outside the domain of knowledge. They do 

 not rest on religious grounds. . . . Looking 

 over the history of human thought, we see 

 the attempt to fasten to Christianity each 

 decaying behef in science. That the earth 

 is round, that it moves about the sun, that it 

 is old, that granite ever was melted — all 

 these beliefs, now part of our common 

 knowledge, have been declared contrary to 

 religion ; and Christian men who knew these 

 things to be true have suffered all manner 

 of evil for their sake." A short sketch of 

 the life of Darwin is prefixed to the essay. 



Researches on Diamagnetism and Magne- 

 Crystallic Action. By John Tyndall, 

 D. C. L., LL. D., F. R. S. New York : D. 

 Appleton & Co. Pp. 288. Price, $1.50. 



The researches embodied in this volume 

 cover the first six years of Prof. Tyndall's 

 experimental work. The first investigation 

 of the series treats of the deportment of 

 crystals, and of other bodies possessing a 

 definite structure, in the magnetic field. 

 Pliicker had discovered that deportment, and 

 had attempted to account for it by sup- 

 posing new forces and new laws. Faraday 

 followed and corroborated Pliicker, and add- 

 ed one more hypothetical force. These 

 forces were held to be wholly distinct from 

 magnetism and diamagnetism. Tyndall and 

 Knoblauch found a much simpler way of 

 accounting for the phenomena observed, 

 which, in place of the assumption of three 

 new forces, required only a simple modifica- 

 tion of known forces, to which they gave the 

 name elective polarity. Prof. Tyndall's first 

 investigation on the subject of diamagnetic 

 polarity is described in the " Third Memoir " 

 of this volume. Supplied with more ade- 

 quate apparatus and material, he prosecuted 

 the research as recorded in the " Fourth Mem- 

 oir," subjecting the deportment of diamag- 

 netic bodies to an exhaustive comparison 

 with that of magnetic bodies, which showed 

 that the diamagnetic force had the same 

 claim to be called a polar force as the mag- 



netic. In the " Fifth Memoir " are described 

 experiments made with a very delicate ap- 

 paratus, which proved that the theory of 

 diamagnetic polarity would stand the severest 

 tests. The application of the doctrine of 

 polarity to magne-ciystallic phenomena is 

 the subject of the "Sixth Memoir." Ap- 

 pended to these papers are letters by We- 

 ber, Faraday, and Tyndall, relating to the 

 investigations, together with some brief de- 

 scriptions of apparatus. 



Journal of Morphology. Yol. II, Xo. 1. 

 Boston: Ginn & Co. Pp. 190. 



This number of the " Journal " contains 

 five papers. The first is a brief account of 

 " Observations on the Structure of the Gus- 

 tatory Organs of the Bat ( VcspertiUo suhula- 

 ius),''^ by Frederick Tuckerman, M. D. This 

 is followed by a paper by Prof. E. D. Cope, 

 " On the Tritubercular Molar in Human Den- 

 tition." Prof. Cope has investigated the 

 variation in the number of tubercles form- 

 ing the crown of the superior true molars in 

 man, and has concluded that " the quadri- 

 tubercular type of molar crown, illustrated 

 by the first superior true molar of man, be- 

 longs to the primitive form from which all 

 the crest-crowned (lophodont; molars of the 

 hoofed placental mammals have been de- 

 rived ; and second, this quadritubercular type 

 of molar has itself been derived from a still 

 earlier tritubercular crown by the addition 

 of a cusp at the posterior internal part of 

 it." He says, further, that " the trituber- 

 cular superior molars of man constitute a 

 reversion to the dentition of the LcmuridcB 

 of the Eocene period of the family of Anap- 

 tomorphidce ; and, second, that this rever- 

 sion is principally seen among the Eski- 

 mos, and the Slavic, French, and American 

 branches of the European race." In the low- 

 est existing races the quadritubercular type 

 predominates, while the neolithic dentitions 

 examined are of an intermediate character, 

 thus showing a superior position to these 

 races. The third paper is by C. 0. Whit- 

 man, on " The Seat of Formative and Re- 

 generative Energy," and deals with the ques- 

 tion whether the cytoplasm is a passive 

 body, moving only as it is acted upon by 

 external forces and influences emanating 

 from the nucleus, or whether it has powers 

 of its own which make it capable also of au- 



