Experimental Evolution, Variation, and Heredity 107 



It shows that even in the case of invertebrate animals acquired habits, produced by 

 social evolution, often determine the form of selection, and so have an important 

 influence on the innate (i. e., racial) characters that are permitted to survive; thai 

 members of the same species exposed to the same environment in isolated groups 

 will often arrive at different methods of dealing with the environment, and so sub- 

 ject themselves to divergent forms of selection; and that the power of accommo- 

 dation to sudden changes in the environment sometimes saves the group from ex- 

 tinction, till "coincident variations" have time to arise, giving complete adaptation 

 to the new conditions, through what may be called coincident selection. 



No. 11. NEWCOMB, SIMON. A Statistical Inquiry into the Probability of Causts of 

 the Production of Sex in Human Offspring. Octavo, 34 pages. Pub- 

 lished 1904. Price $0.25. 



The above paper is an attempt to apply a rigorous theory of probable inference 

 to questions of genetic biology, taking statistical data as the basis of the inquiry. 

 The author in this case strayed outside his professional field and undertook this 

 work with the belief that the treatment of statistical data generally on a large scale 

 by the methods of probable induction would lead to important results to the science 

 of the future and to conclusions on questions which elude all direct investigation. 

 Among the topics discussed are "Preponderance of male births," "Is the ratio of 

 male to female births the same in all races?" "Inquiry whether any unisexual 

 tendency exists among parents," "Unisexual tendency in multiple births," "Pro- 

 cesses suggested by the statistics of multiple births," "Influence of the age of the 

 parent on sex," "Supposed influence of other conditions," "Mathematical theory of 

 the effect of unisexual tendency." 



No. 36. STEVENS, N. M. Studies in Spermatogenesis. 



Part I. Studies in Spermatogenesis, with special reference to the "Accessory 

 Chromosome." Octavo, 32 pages, 7 plates. Published 1905. Price $0.25. 



Part II. A Comparative Study of the Heterochromosomes in Certain Species of 

 Coleoptera, Hemiptera, and Lepidoptera, with especial reference to sex deter- 

 mination. Octavo, 33-74 pages, 8 plates. Published 1906. Price $0.25. 



Part I is a comparative study of the Spermatogenesis of Termopsis angusticollis, 

 Stenopelmatus sp. (?), Blatella germanica, and Tenebrio molitor. No "accessory" 

 was found in Termopsis. Further study of more favorable material of Stenopelma- 

 tus has shown the spermatogonial number of chromosomes to be 47 (instead of 46), 

 and the numbers in the second spermatocytes to be 23 and 24. 



Part II comes along the line of investigation suggested by the study of Tene- 

 brio molitor. The Spermatogenesis of 18 species of Coleoptera, in which an unequal 

 pair of heterochromosomes is found, is described, and also 4 species which have an 

 unpaired heterochromosome. In every case where it was possible to study the chro- 

 mosomes of the female, an equal pair of heterochromosomes was found correspond- 

 ing to an unequal pair of an unpaired heterochromosome in the male. 



No. 51. STEVENS, N. M. Studies on the Germ-cells of Aphids. Octavo, 28 pages, 



4 plates. Published 1906. Price $0.25. 



This is a comparative study of the germ-cells of 22 species of aphids, showing 

 great variety in number and size of chromosomes in the various species. No re- 

 duction in number of chromosomes was found in the parthenogenetic eggs, which 

 always showed a pair of chromosomes corresponding to each chromosome of the 

 spermatocytes or polar spindles. No heterochromosomes were found, but it has 

 since been determined that the "lagging" chromosome described in this paper is an 

 unpaired heterochromosome, and that the spermatocytes which do not contain a 

 heterochromosome degenerate and only "female-producing" spermatozoa mature. 



No. 19. ENTEMAN, WILHELMINE M. Coloration in Polistes. Octavo, 88 pages, 6 

 colored plates, 27 text figures. Published 1904. Price $1.00. 



A study of one of our commonest wasps dealing with the variations of its colors 

 and color pattern, the ontogenesis of the color pattern, and the geographic distribu- 

 tion of the types of color marking. All of these facts are considered in relation 

 to the various theories of evolution. 



