196 TRANSACTIONS OF THE SOCIETY OF 



possible to establish all the requisite transitions between the two extremes of 

 this family, extremes which may be represented by the slug, (inteinial shell,) 

 and the snail, (external shell.) M. Victor Fatio communicated a memoir on the 

 vertical distribution of species in certain families of birds. Leaving the basin 

 of Lake Leman with twenty-four different species of sylviadaj, he loses some 

 one of these species in proportion as he ascends the mountains ; and when 

 arrived at the Haute-Eugadine finds himself accompanied only by redstarts, one 

 of which alone, the ruticilla titlujs, ascends still higher. In this comparative 

 study, the author first establishes an approximation between the north pole and 

 our higher Alps, which leads him to signalize the relations which exist, for birds, 

 between their horizontal passages and vertical migrations. Next, passing to 

 this transport of species to heights more and more considerable, he i-ecoguizes 

 the influence which climate and the nature of the soil exercise on the produc- 

 tion of nourishment. 



Verbal reports. — M. V. Fatio took notice of the appearance at Geneva of a 

 bird, the si/oraptcs paradoxus, which inhabits Siberia, Tartary, and China, and 

 which entered Europe in 1SG3, directing its course from the northeast of Ger- 

 many to the southwest of France. An extraordinary drought in its native 

 country has probably been the cause of this unusual migration of the bird in 

 question. 



Anatomy and Physiology — Memoirs. — Professor Thury communicated his 

 important memoir on the law of the production of sexes. In the case of plants, 

 the fundamental identity of the pistils and stamens is admitted by those 

 botanists who regard the organs in question as modified leaves. Now, accord- 

 ing to the experiments of Knight, heat favoring the production of male flowers 

 in dioecious plants, M. Thury has thence concluded that the caloric acted on 

 plants by occasioning a more complete elaboration and maturation of the juices 

 and organs, so that the production of tlie male element would correspond with 

 a more perfect development of the genu. Apjilying these ideas to the animal 

 kingdom, our colleague has deduced from them the consequence, that the pro- 

 duction of one or the other sex depends only on the degree of maturation of 

 the egg, a maturation which would continue to advance during the time which 

 -elapses between the moment of the detachment of the ovum and that of its 

 impregnation, in such manner that the ova promptly fecundated would yield 

 i'emales, and those more slowly fecundated males. Such is the filiation of ideas 

 by which M. Thury has arrived at the theory to which his name will remain 

 attached ; a theory which was confirmed by experiment in each of the twenty- 

 nine cases in which, at the instance of its author, trial was made by M. Cornay. 

 These ideas of our colleague have excited very general interest ; they were 

 immediately submitted to investigation in France, in England, and in Germany, 

 .and this on so large a scale tiuit we may hope to arrive promptly at results 

 altogether decisive. Certain objections, however, have been raised against this 

 tlieory, of which we shall here notice only such as have been advanced at our 

 own sittings. Thus, for instance, in regard to hemp, which grows in very 

 different climates, it has been said that nothing has heretofore indicated that 

 more male individuals are produced in the hemp of warm countries than in that 

 of cold ones. Again, M. Pagenstecher has sought to demonstrate that the 

 theory of M. Thury was in opposition with observations on the parthenogenesis, 

 and he substitutes for it another theory, in which account is equally taken of 

 the age of the q^^ at the moment of its fecundation. In effect, at the session 

 of the Helvetic society of natural sciences in 18G3, he expressed the idea that, 

 by maturation, the pellicle of the ovule became hardened, which might prevent 

 a more or less considerable number of zoospermes from penetrating into the in- 

 terior of the Q^^, and thus influencing its sexuality. Some of these objections, 

 it must be confessed, rest only upon bypothcaes and need demonstration in 

 order to obtain assent. 



