170 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Epithelium of Stomach.* — M. C. Dekhuyzen and P. Vermaat have 

 studied the epithelium lining the stomach in rats, mice and rabbits. 

 Some of the cells have the power of sending out a large number of cell- 

 filaments, which stand closely together when the striated horde]' is 

 contracted and when the filaments have their minimum length, hut 

 which can also be extended, and are then enabled to diverge. The " outer 

 limbs" vary greatly in appearance, now more hair-like, and again less 

 delicate. Like similar cells in the intestine, they are apparently absorp- 

 tive, for some showed small drops of fat. 



Peculiar Osseous Tissue of Sunfish.f— Felice Supino describes 

 afresh the peculiar hony tissue of Ortliagoriscus, which is so soft that it 

 can he readily cut with a razor. It is quite distinct from cartilage, and 

 exhibits a sort of network, in the meshes of which there is an amorphous 

 hyaline substance, not readily stainahle (non-calcified ossein according 

 to llarting), including a few cells and numerous long and tortuous 

 fihres. 



Minute Structure of the Suprarenals in Guinea-Pig.J — Franz 

 Puhrmann distinguishes sharply between the external cortical layer (zona 

 glomerulosa and part of the zona fascicularis of Arnold) and the internal 

 cortical layer (zona reticularis) of Arnold. The medullary area consists 

 of internal cortical cells in a different functional state. The detailed 

 characters of the elements of the external and internal layers are described 

 at length. 



Eyelids of Mammals.§— H.Eggelinghas made a comparative study 

 of mammalian eyelids, which are primarily folds of the integument 

 clothed externally and internally with many-layered flat epithelium, hairs, 

 and skin-glands. Internally, the integumentary characters are mostly 

 lost, but the many-layered flat epithelium may have considerable 

 development, and meibomian glands arise from sebaceous glands near 

 the margin. The so-called tarsus, a firm differentiation of the connec- 

 tive tissue, within which the meibomian glands lie, is characteristic 

 of quadrumana. Much of the increased differentiation in mammals, as 

 compared with other vertebrates, is due to the increased development of 

 the eye musculature. 



c - G-eneral. 



Formation of a Species. ||— J. F. Walker discusses what takes place 

 when one species is changed into another. When the species A is con- 

 verted into the species B, there must be an intermediate transitional 

 stage, in which the collection of individuals is neither the species A nor 

 the species B. A species is defined as a centre round which individuals 

 are thickly clustered, and the spaces between these centres may be either 

 devoid of individuals or contain here and there an abnormal form. The 

 true type of a species is its centre, where the individuals are most thickly 

 clustered and most closely resemble each other ; those further from the 



* K. Akad. Wetenschappen Amsterdam (Proc. Sect. Sci.) vi. (1903) pp 30-4 



t Atti. R. Accad. Lincei (Rend.) xiii. (1904) pp. 118-21. 



J Zeitschr. f. wisa. Zool., lxxviii. (1905) pp. 522-M (2 pis.). 



§ Jenaische Zeitschr. f. Naturwiss., xxxix. (1904) pp 1-42 (IS fi°-s ) 



|| Geol. Mag., Decade V., ii. (1905) pp. 15-17. ° 



