ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 537 



the spinal cord, etc. — medulla and muscle centres for the region of the 

 vertebral column and extremities, exciting these centres more or less, 

 but always only weakly. 



Brain Development of Sexes in Twins and Triplets.* — H. 

 Waldeyer found in three cases of twins of opposite sexes that the brain 

 of the male fcetus in each <;ase showed a more advanced stage of 

 development. This was the case also in one instance of triplets ; in two 

 other instances of triplets this difference could not be recognised. 



c. 



Greneral. 



Variation in the Dentition of the Dog.j — J. Kunstler and J. Chaine 



report a case where the upper jaw bore 4 regular incisors, so that the 



4 1 3 3 



formula was i -, c -, pm -, m -. The authors refer to other cases in 

 3 1 4 3 



which 43, 44, 46 and 47 teeth have been recorded. 



Skin of North Atlantic Whales.| — Arnold Japha gives an account 

 of the skin and skin structures of Megaptera and of Balcenoptera. The 

 integument consists of epidermis and sub-epidermal tissue corresponding 

 to the cutis and sub-cutis of other mammals. In the sub-epidermal tissue 

 there is the blubber layer with a thin upper stratum similar in structure 

 to the corium of other mammals, but not entirely free from fat. The 

 fat-cells of the blubber layer occupy the wide meshes of connective-tissue, 

 and are very large. Elastic fibres are abundant. The upper surface of 

 the sub-epidermal tissue rises into narrow ridges, arranged generally 

 longitudinally, and whose structure varies in different species. On 

 these ridges rest the elevated papillae, containing almost the only blood- 

 vessel loops which nourish the epidermis. The thickness of the 

 epidermis varies with the species, and consists of five layers : a layer of 

 small cubical cells at the bottom, next one of long spindle cells, a middle 

 layer of large polygonal cells, one of flat spindle cells, and a horny layer. 

 Horn is present, but neither keratohyalin nor eleidin could be demon- 

 strated. The pigment in the coloured animals is confined to the 

 epidermis, and occurs in two forms. It is present in all the layers of the 

 epidermis, forming caps around the nucleus and as much-branched 

 stellate chromatophores in the lowest layer. Sweat and sebaceous glands 

 are absent. In adults hairs are constantly present in a definite arrange- 

 ment on the head, but absent on the rest of the body. The hair 

 papillae are compound ; moulting of the hair appears not to take place. 



Lungs of Cetacea.§ — F. E. Schulze has examined the lungs of 

 dolphins and of two right-whales. In dolphins there is a remarkable 

 development of cartilaginous framework extending into the respiratory 

 parenchyma. On each of the surfaces of both sides of the relatively 

 thick alveolar septs there extends a special respiratory capillary net. In 

 the right-whales the cartilages do not extend so far into the respiratory 



* S.B. k. Preuss. Akad. Wiss. Berlin, vi. (1907) pp. lU-26. 

 t Proc. Verb. Soc. Sci. Bordeaux, 1906, pp. 26-7. 

 X Zool. Jahrb. Abt. Anat., xxiv. (1907) pp. 1-40 (7 pis.). 

 § SB. k. Preuss. Akad. Wiss Berlin, x. (1907) p. 203. 



