24 SUMMARY OF CURRENT RESEARCHES RELATING TO 



range, but the general interest is twofold. In the first place a com- 

 parison with Hochstetter's account of the development of the vena cava 

 posterior of Echidna aculeala suggests that the course of development 

 of the vein is substantially the same in the two forms, and that the 

 variations in DideJphys are produced by an arrest of development at 

 various stages. In the second place, it is of interest to note that 

 Mr. Oldfield Thomas believes that D. virginiana is merely a variety of 

 the very variable D. marsupialis, and. states that the variability of the 

 opossums generally is such that specimens even from the same locality 

 show " an entire absence of constancy in any character or set of 

 characters." The reference in the quotation is of course to the external 

 characters. 



Respiration in Lungless Salamanders.*— Miss A. I. Barrows has a 

 brief note on the respiratory organs of Desmognathus fusca. She finds 

 that the skin contains a network of capillaries, and similar networks are 

 present in the mouth and pharynx. Further, the entire wall of the 

 oesophagus is furnished with a network of cajnllaries, which lie in the 

 epithelium, and. are probably of great respiratory significance in this 

 lungless form. 



'o 



Forked Tails in Amphibians. f — Dr. G. Tornier has studied many 

 cases, and draws a number of conclusions. The degree of super- 

 regeneration in a region depends on the size of the wound. Forked 

 tails in natural conditions may be legitimately regarded as the results 

 of wounds, since exactly analogous states can be induced experimentally. 

 When regenerative processes set in, the basal parts of the integumental 

 structure are the first to be laid down in rudiment, and the apical regions 

 later on ; but with the skeletal parts the process works in the opposite 

 direction. Because of this there arise two-pointed lizard-tails in which 

 the skeleton of one of the points seems to wane away towards the axis. 

 That growth at first abnormal may be corrected is due not to " self- 

 regulation," but to inequalities of growth. 



Abnormalities in Lepidosiren.J — Mr. H. H. Brindley describes par- 

 tial duplicity of the limb or sudden tapering into a sharp tip, abnor- 

 malities in all probability of regenerative growth after injury. In the 

 repair of an injury there is a special proliferation at one point, and the 

 epidermis makes haste to cover the exposed, subjacent tissues. Thus 

 the trophic events of growth proceed otherwise than in normal develop- 

 ment, and extremely slight circumstances may affect the direction of 

 growth. In the absence of the co-ordination of growth which obtains 

 in normal development, external interference may in some cases mould 

 the regenerating structure in a special form. 



Teeth and Breathing- Valves of Fishes.§ — Mr. E. Phelps Allis, jun., 

 has investigated the structure of the mouth-cavity in Polypterus bicMr, 

 with special reference to such questions as the homologies of the teeth 

 and the parts of the palate in Fishes and Amphibians. Of the two rows 



* Anat. Anzeig., xviii. (1900) pp. 461-4 (2 figs.). 



t Zool. Arizeig., xxiii. (1000) pp. 233-56 (12 figs.). 



% Proc. Cambridge Phil. Soc, x. (1000) pp. 325-7 (1 pi.). 



§ Anat. Anzeig., xviii. (1000) pp. 257-89 (3 figs.). 



