528 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Structure of Swim-bladder of Umbra.* — M. Rauther describes the 

 minute structure of this organ in Umbra pygmsea, a fish that has an 

 inadequate branchial apparatus and uses the swim-bladder when it is out 

 of water. It can remain out of water for nine hours without suffering 

 more than transient bad effects. 



The swim-bladder is a long sack with delicate walls extending under 

 the backbone for the greater part of the body cavity. Anteriorly there 

 is a longitudinally plaited expansible pneumatic duct, opening in a deep 

 groove on the dorsal surface of the gut behind the last gill-cleft. The 

 swim-bladder shows an internal epithelium with which capillaries are 

 closely associated, a dense layer of connective tissue, a simple layer of 

 longitudinal smooth muscle-fibres, a thick loose layer of connective 

 tissue, and a strong layer of circular smootb muscles. The anterior end 

 shows remarkable vascular plexuses or retia mirabilia, both arterial and 

 venous. There is no gas gland. The posterior portion of the swim- 

 bladder receives most of its blood from the intercostal arteries. The 

 highly vascularized epithelium in Umbra points indubitably to a respir- 

 atory function. 



Vascular System of Myxine.t — F. J. Cole communicates some 

 account of the cardinal veins, the venous trunks associated with the 

 heart, the sub-intestinal vein, and so on. The feature of greatest 

 interest in the Myxinoid vascular system is the extensive series of spaces 

 now known as veno-lymphatics. In Myxine they always contain blood 

 in considerable quantity, and there are grounds for believing that they 

 are only enlarged veins, and not comparable with the true lymphatics of 

 higher animals. Blood enters the peribranchial sinuses from the afferent 

 branchial arteries and the contents of these sinuses must drain posteriorly 

 into the inferior jugular vein. 



Vascularization of Skin in Newts.f — R. Despax has made a histo- 

 logical study of the skin of a Pyrenean newt {Triton asper Duges), with 

 a view to determining the importance of cutaneous respiration. He 

 found that the capillaries were very closely associated with the epidermic 

 epithelium. In Triton asper the thickness of the integument is relatively 

 greater than in other species of the same genus. The epidermis, in the 

 region where it is thickest, includes, in addition to the two-layered 

 stratum corneum, four or five layers of epithelial cells. The nuclei of 

 the deepest layer of epithelial epidermic cells are oval, with the long 

 axes directed at right angles to the surface of the skin ; those of the 

 median layers are more or less regularly spherical, while those of the 

 lower layer of the stratum corneum are flattened. The average thick- 

 ness of the dermis is at least equal to, and sometimes greater than that 

 of the epidermis above it. It attains its greatest thickness in the space 

 between the cutaneous glands. In the most superficial region of the 



* Zoo]. Jahrb. Abth. Allg. Zool., xxxiv. (1914) pp. 339-64 (10 figs.). 



t Anat. Anzeig., xlvi. (1914) pp. 478-85 (1 fig.). 



% Bull. Soc. Zool. France, xxxix. (1914) pp. 215-221 (2 figs.). 



