ZOOLOGY AND BOTANY, MICHOSUOPV, ETC. 31 



mode of development was seen in both kinds of gland (large aud small) 

 in the salamander's skin. The large poison-glands must be described 

 as more perfectly differentiated towards a special function. Dr. Ancel 

 maintains that even the smooth muscle-fibres which penetrate into the 

 epidermis arise from epidermic cells; they do not assume their elongated 

 form until the bud has penetrated into the dermis, and they remain (in 

 the adult) united to neighbouring epidermic cells by protoplasmic 

 bridges. 



Structure of Herbst's Corpuscles in the Sparrow and Fowl.*— 

 Guido Sala, by the use of chloride of gold, has succeeded in demonstrating 

 that the stroma of these corpuscles does not consist, as has been hitherto 

 supposed, of the union of concentrically arranged lamellae of connective 

 tissue, but is formed of a thick network of skein-like twisted fibres, in 

 whose meshes the connective-tissue cells are placed. 



c. General. 



Chemical Basis of Variation.!, — Armand Gautier returns to the thesis 

 of a well-kuown memoir which he published in 1886, — that the variations 

 which mark the beginning of a new variety are detectable even in the 

 chemical composition of the cells, and that they may appear suddenly 

 without intermediate steps. He brings for ward some fresh facts support- 

 ing this view. The plant or animal organism may exhibit important 

 variations with some abruptness ; these variations have their basis in 

 changes in the plasmic molecules of particular organs, and these plasmic 

 changes are referable to the reciprocal influence of other plasmas, and to 

 a less extent to changes in environment and nutrition. 



Two States of Living Matter.:}: — Felix Le Dantec argues in support 

 of the hypothesis that there is a fundamental and widespread occurrence 

 of cellular dimorphism, of units with n chromosomes and units with 2 n 

 chromosomes, as seen in the contrast between the cells of sporophyte and 

 gamophyte in ferns, between somatic cells and germ-cells in animals. 

 He applies his idea to the phenomena of maturation and fertilisation. 



Effect of Light on Animals. § — Prof. W. A. Nagel gives a critical 

 resume of recent research on this subject, with special reference to the 

 comparisons which have been made between plants and animals in respect 

 to their reaction to light. He applies the term phototropism to the 

 peculiarity displayed by many sedentary organisms or special organs, of 

 taking up a fixed position in regard to light, by means of bending 

 movements, movements of growth or of torsion. On the other hand, 

 phototaxis is the peculiarity displayed by free-swimming organisms of 

 orienting the body so as to place its long axis in a definite relation to the 

 direction of the rays, and of retaining ibis position, if movement ensues, 

 during progression through the surrounding medium. In both cases a 

 positive and negative form of the phenomena can be distinguished. 

 Eothert has given the name of " apobatic phototaxis " to that suscepti- 

 bility to alterations of intensity (Unterschiedsempfindliclikeit) which is so 

 pronounced in, e.g. Amphioxus, many tube-inhabiting worms, burrowing 



* Anat. Anzeig., xis. (1901) pp. 095-6 (1 pi.). 



t Connotes Kendus, cxsxiii. (1901) pp. 570-2. J Tom. cit., pp. 698-700. 



§ Bot. Ztg., lix. (1901) pp. 289-99. 



