218 SUMMARY OF CURRENT RESEARCHES RELATING TO 



third is seen in its neiglibom-liood ; the post-anal enteron, which 

 primitively has no communication with the medullary tube, obtains one 

 by the latter bending down around the hinder end of the notochord. 

 Later on, this connection also disappears, and the post-anal enteron 

 becomes absorbed. Similar observations are recorded as having been 

 made on various other birds, but the author refrains for the present 

 from any distinct generalizations. 



In his second (4:th) paper, Dr. Braun states that as the post-anal 

 enteron is absorbed, a circular constriction is developed vertically to 

 the long axis of the tail ; this becomes gradually nipped off, and forms 

 a knob of tissue, which is connected by a narrow stalk with the true 

 body of the tail ; this decreases in size, and at last consists only of 

 a small collection of ectodermal cells. 



The notochord undergoes a special set of changes at the tip of the 

 tail ; the hinder end is, in embryonic parrots, long persistent at a 

 lowly stage of development ; there is in it a cord of rounded cells — the 

 notochordal rods. In a number of mammals examined the same 

 structure was detected, and found to constitute a body homologous 

 with the caudal knob of birds just described. These observations lead 

 to the conclusion that, in mammals as well as in birds, the notochord is, 

 so to speak, too long ; no vertebraa are formed around its hinder end. 

 In the Amphibia (Urodela at any rate) the chorda would seem to be too 

 short, if the observations of Flesch and Fraisse are correct. 



Epidermis of Salamander.* — Dr. Pfitzner, previously the author 

 of a dissertation on Leydig's cells in the stratum mucosum of the 

 larva of the spotted salamander, now publishes a detailed review of 

 the epidermis of this animal. In accordance with Flemming, he first 

 sets forth the excellence of the salamander as a subject for the histo- 

 logist (to whom it should be no less valuable than the frog to the 

 physiologist), and gives a brief opening account of its breeding, with 

 hints as to its maintenance during captivity. A further introduction 

 deals with methods of preparation. The bulk of the memoir is 

 occupied by tn^o sections on (1) the larval, and (2) the adult form. 

 In conclusion, the epidermis of the salamander, as exemplifying its 

 class, is compared with that of fishes and the higher vertebrates from 

 a physiological point of view. 



At all periods of post-embryonic life, the epidermis of Salamandra 

 includes the two usual strata. In the newly-born larva each of these 

 is made up of but a single tier of cells, nor does the stratum corneum 

 ever consist of more. According to our author, the same is the case 

 with the frog (and probably all batrachians). The upper larval 

 layer has a striated cuticular border, representing an earlier invest- 

 ment of cilia. As the time of metamorphosis approaches, the whole 

 depth of the cell is gradually cornified, and the primitive upper 

 stratum is then ready to be cast off. During the second month of 

 larval life, the cells of the stratum mucosum appear two deep ; a 

 month later, there are three irregular tiers of these cells. In the 

 fourth month the cells of the upper tier of the inner stratum change 



* Morph. Jahrb. (Gegcnbaur), vi. (1880) pp. 469-526 (2 pis.). 



