306 



SCIENCE. 



[N. S. Vol. XXII. No. 558. 



mosomes in either the male or the female 

 parthenogenetic generations. Reduction in 

 the sexual germ cells is effected by longitudinal 

 pairing of like chromosomes. The behavior 

 of the chromosomes in Aphis exactly fulfils 

 the con,ditions required by Mendel's law of 

 heredity; and their form and size relations 

 oSer support to the theory of the ' individual- 

 ity of the chromosomes.' The results also 

 suggest that sex may be determined in Aphis 

 by a change in dominance of the sex-character, 

 brought about by external conditions. ' Re- 

 generation in Polychoerus caudatus/ by N. M. 

 Stevens and A. M. Boring. So far as regen- 

 eration in Polychoerus has been tested by the 

 authors it seems to be largely a question of 

 ' organization ' and ' totipotence ' of material, 

 modified in many cases by the folding under 

 and uniting of the anterior cut surfaces. His- 

 tological examination of the regenerated parts 

 shows the process to be one of pure morphal- 

 laxis. ' The Relation of the Degree of Injury 

 to the Rate of Regeneration,' by Charles 

 Zeleny. The rate of regeneration of a removed 

 chela of the cray-fish is greater when other 

 appendages are removed at the same time than 

 when it alone is removed. A similar result 

 was obtained with other forms, disproving the 

 common belief that an increase in the degree 

 of injury to an animal lowers its vitality and 

 thereby diminishes its capacity for repairing 

 sustained injuries. ' Studies on Chromo- 

 somes : 1. The Behavior of the Idiochro- 

 mosomes in Hemiptera,' by Edmund B. Wil- 

 son. The author gives an account of the dis- 

 tribution of the chromosomes to the sperma- 

 tozoa in several species of Hemiptera, and 

 shows that two classes of spermatozoa are 

 formed, in equal numbers, which differ only in 

 respect to the size of one of the chromosomes 

 (called the ' idiochromosome'). A discussion 

 is given of the bearing of the facts on 

 Mendelian inheritance, sex-determination, and 

 the origin and meaning of the accessory 

 chromosomes. ' The Movements of the Swim- 

 ming Plates in Ctenophores, with Reference 

 to the Theories of Ciliary Metachronism,' by 

 G. H. Parker. Experiments were made upon 

 Mnemiopsis and Pleurohrachia and the con- 

 clusion reached that transmission of the im- 



pulse to ciliary movement is neuroid in char- 

 acter, though this is probably supplemented 

 by mechanical transmission. ' On a General 

 Theory of Adaptation and Selection,' by 

 Henry Edward Crampton. The ' Principle 

 of the Correlative Basis for Selection ' is de- 

 veloped upon the results of the author's 

 statistical and experimental studies upon 

 saturnid lepidoptera. The principle states 

 that selection proceeds with reference to the 

 condition of correlation of the organism, and 

 that this condition involves the whole series of 

 external influences as well as all the internal 

 ' characters ' of individuals. ' Experimental 

 Studies on the Development of the Eye in 

 Amphibia: II., On the Cornea,' by Warren 

 Harmon Lewis. The cornea will not form 

 without the optic cup or lens coming into con- 

 tact with the ectoderm, and the influence of 

 these organs can cause corneal formation in 

 ectoderm which under normal conditions never 

 gives rise to a cornea. The cornea is neither 

 predetermined nor self-differentiating. 



The July-August number of the Journal of 

 Geology contains an article by Professor W. 

 M. Davis, entitled ' The Geographical Cycle in 

 an Arid Climate,' which he considers under 

 the subheadings of ' initial, youthful and ma- 

 ture stages ' and ' the beginning of old age.' 

 Professor Davis concludes that ' the scheme of 

 the arid cycle thus seems to be as well sup- 

 ported by appropriate facts as is the scheme of 

 the normal cycle.' Mr. E. S. Bastin furnishes 

 a ' Note on Baked Clays and Natural Slags in 

 Eastern Wyoming.' Professor Charles S. 

 Prosser contributes an article on ' The Dela- 

 ware Limestone ' which is the upper formation 

 of the Devonian limestones of Ohio, while the 

 lower one is known as the Columbus limestone. 

 It is shown that the limestone in the northern 

 part of the state, which Newberry named the 

 Sandusky and supposed to be the upper forma- 

 tion, really represents the Columbus and, 

 therefore, the formation name Sandusky is 

 dropped and Orton's later one — Delaware 

 limestone — adopted. Mr. Richard S. Lull has 

 a paleontological paper, entitled " Megacerops 

 Tyleri, a new species of Titanothere from the 

 Bad Lands of South Dakota,' illustrated by 



