November 27, 1914] 



SCIENCE 



115 



The segmentation discussed in the paper is as- 

 signed to changing rates of rotation, the most 

 powerful agency of deformation to which the 

 earth is subject. The first order of deformation 

 under rotation, the passage from a sphere to an 

 oblate spheroid, is passed hastily as familiar 

 ground, save that an analysis is offered of the 

 mode by -which an earth-body of crystalline tex- 

 ture, affected by a concentric structure, arising 

 from accretion, and a radial structure, arising 

 from vulcanism, would respond to the varying 

 stress-demands imposed by changing rates of ro- 

 tation. This first order of deformation or seg- 

 mentation proceeds by halves acting reciprocally, 

 its basis being the simplest of divisors, two. The 

 essence of the paper consists in showing that 

 when such bipartite division is extended to the 

 second order of segmentation it develops me- 

 chanical inadaptabilities, but that a second order 

 of segmentation on the basis of the next simplest 

 divisor, three, results in working adaptations. 

 This order of segmentation gives rise to six see- 

 tors of similar form arranged symmetrically rel- 

 ative to -the axis of rotation and alternately re- 

 specting the sectors of the opposite hemisphere. 

 The special adaptability of this segmentation to 

 ease the stresses that arise from changes in the 

 rates of rotation is pointed out, as also certain 

 causal relations that exist between these sectors 

 and their essential parts. The surficial expression 

 of these sectors is identified with the great physio- 

 graphic features of the earth's surface. 



VI. Botany Bacteriology 



Chaeles E. Allen: Development of the Male 



Germ Cells of Polytrichum. 



At the conclusion of the antheridial divisions, 

 each cell contains a blepharoplast which behaved 

 like a centrosome in the last division. This 

 blepharoplast begins to elongate. At about the 

 same time a large spherical body, the limosphere, 

 appears, variously situated in the cytoplasm; 

 later it comes to lie near one (the anterior) end 

 of the blepharoplast. The blepharoplast is now in 

 contact with the plasma membrane; two long cilia 

 grow out from its anterior portion. The nucleiis 

 elongates in the same direction as, and in contact 

 with, the blepharoplast. The limosphere divides 

 into two bodies; the smaller remains in contact 

 with the anterior end of the blepharoplast; the 

 larger lies close to the posterior part of the 

 nucleus. The nucleus becomes a long, coiled, 

 finally homogeneous body, of about one and one 



half turns. The cytoplasm contains another body 

 of variable size, often lying in a vacuole, which is 

 recognizable from a time a little later than the 

 appearance of the limosphere until nearly the 

 completion of the metamorphosis of the nucleus. 

 During this history the cell becomes first approxi- 

 mately spherical, then lens-shaped. The cyto- 

 plasm, aside from the special bodies mentioned, 

 gradually decreases in amount. The body of the 

 mature antherozoid consists of the nucleus, with a 

 short portion of the blepharoplast, bearing the 

 cilia, at its anterior end. The rest of the blepha- 

 roplast has become indistinguishable. Adhering 

 to the posterior end of the nucleus, but not a part 

 of the body of the antherozoid, are the remains of 

 the cytoplasm, including the larger derivative of 

 the limosphere. 



Chakles J. Chambeblain: A Phylogenetic Study 

 of Cycads. 



The cycads, as the only surviving family of an 

 ancient phylum reaching back into the Paleozoic, 

 are peculiarly favorable for phylogenetic study, 

 and the work of others upon the Paleozoic and 

 Mesozoic predecessors of the modern family adds 

 to the opportunity for comparison. The nine liv- 

 ing genera of the Cycadaceas are confined to trop- 

 ical and subtropical regions, chiefly Mexico, Cuba, 

 Australia and South Africa, but during the past 

 ten years all the genera and many of the species 

 have been studied in the field, and material has 

 been collected for a somewhat complete study of 

 life histories. The accounts already published have 

 dealt with cycads in the field and also with cyto- 

 logioal details of development and have been de- 

 scriptive rather than theoretical, the natural tend- 

 ency to discuss the comparative morphology and 

 phylogeny of the phylum being restrained for the 

 present. Cytological features have proved to be 

 more uniform and distinctive than the characteris- 

 tic habit of the family. 



The investigation, as it stands, adds support to 

 the already strong conviction that the Cycado- 

 filicales, Beimettitales and Cyeadales constitute a 

 single phylum; when completed it may throw some 

 light upon variation, development and retrogres- 

 sion. 



Wm. Crockeb and J. F. Gkoves: Method of De- 

 termining the Life Duration of Seeds. 

 In most seeds in a dry condition the viability 

 persists from 1 to 150 years, varying with the* 

 species. There have been several explanations 

 offered for the loss of viability. Exhaustion of 

 food by respiration, degeneration of digestive and 



