,J(i \i.\l.\l;Y OF CURRENT RESEARCHES RELATING TO 



Origin of Notochord Epithelium.* — W. Georgi found in embryos 

 of Necturus that the primitive notochord-cells (Urchordazellen) produce 



the elastica externa. Thereafter, but while it, is still very fine, sen- 



i-liy cells pass through it into the notochord and form the epithelium. 



From the epithelium, and therefore of mesodermic origin, there are 

 formed two other sheaths, the fibrous sheath and the elastica interna. 

 Alter the latter is formed there is no further immigration of mesenchyme 

 cells possible. The notochord cartilage, which takes the place of the 

 primitive notochord, is also due to the chorda-epithelium. 



Development of Myotomes.! — A. L. J. Sunier has studied the firsl 

 stages in the internal differentiation of myotomes and the formation of 

 sclerotomatic elements in Acrania, Selachians, and Teleosts. The un- 

 differentiated elements of the wall of the myotomes become partly 

 muscular, partly mesenchymatous (connective in Acrania). The prim- 

 ordial elements of the musculature are cells in the form of plates, which 

 afterwards become split up longitudinally into fibres. The formation of 

 sclerotomatic elements in Craniata is simply the dissolution of a portion 

 of the median wall of the myotome. The scleroccel of Selachians is the 

 space which remains between the median wall and the rounded ventral 

 end of the muscular mass. It has no connexion with the formation of 

 sclerotomatic elements, and it is quite different from the altogether 

 special scleroccel of Amphioxus. It seems very doubtful if the " external 

 layer " of the mesoderm has the same significance in different Vertebrates. 



Role of Interstitial Testicular Cells 4 — L. Mazzetti has studied 

 these elements in a variety of types, such as frog, bird, dog, and man. 

 He finds that the interstitial cells are unquestionably of connective- 

 tissue origin, being transformations of connective cells which proliferate 

 between the tubules. They may also arise, and perhaps in greater part, 

 from lymphatic lacuna 1 . They have either no importance or only a 

 minimal importance in connexion with secondary sex-characters. These 

 are determined by re-absorption of seminal fluid, including both sperm- 

 cells and their secreted products. 



b. Histology. 



Spindle-cells of Amphibian Blood.§ — E. Neumann maintains that 

 the erythrocytes arise in part from the colourless spindle cells, and that 

 there is a continuous series of transition types between spindle-cells and 

 lymphocytes. 



Eye ofPteropus.|| — Gustav Fritsch describes a remarkable peculiarity 

 of the eve of Pteropus condorensis, similar to that also discovered by 

 Kohner in P. medius, namely, that the choroid sends long finger-like or 

 spindle-shaped (not conical) processes into the middle layers of the 

 retina. His description differs considerably from Kolmer's. 



* Auat. Anzeig., xxxviii. (1911) pp. 176-87 (4 figs.). 



+ Onderzoekingen Zool. Lab. Rijksuniversiteit Groningen, ii. (1911) pp. 1-99 

 (6 pis.). % Anat. Anzeig., xxxviii. (1911) pp. 361-87 (14 figs.). 



§ Arch. Mikr. Anat., lxxvi. (1911) pp. 725-44. 

 II Zeitschr. wias. Zool., xcviii. (1911) pp. 288-96 (1 pi.). 



