ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 27 



but is a structure of transitory nature. The root of the tongue develops 

 from the ventral ends of two visceral arches, the third arch playing no 

 part in its formation. The large salivary glands develop in the follow- 

 ing order : — parotid, suh-maxillary, sub-lingual. 



Development of Pig's Intestine.* — Dr. J. B. MacCallum has dis- 

 sected numerous pig embryos of sizes varying from 12 mm. to 12 cm. 

 The various loops were modelled with copper wire. At an early stage 

 the gut consists of an uncoiled tube which sends a single loop out into 

 the coelom of the umbilical cord. The first half of the loop is on the 

 right side, and gives rise to the small intestine. From the other half is 

 formed the large intestine. The gut increases in length by the forma- 

 tion of regular loops, which grow around an axis corresponding with 

 that of the cord and the large intestine. These loops form first in the 

 part which is to become the small intestine. They also develop in the 

 part of the small intestine near the stomach before they appear in the 

 cord. Up to a certain stage the further growth in complexity is greatest 

 near the stomach. After the small intestine has become considerably 

 coiled, a mass of loops is formed in the large intestine. In embryos 

 between 35 mm. and 40 mm. in length the group of coils which has 

 formed in the coelom of the cord enters the general body-cavity by a 

 mechanism which is not clearly understood. In embryos of the above 

 sizes the coils are constant in arrangement and definite in their posi- 

 tion ; in older embryos the groups of coils always hold the same relative 

 position in the body. These groups arrive at their final situation by a 

 rotation which takes place posteriorly and to tho right round an axis, 

 running from the beginning of the duodenum to a point a short distance 

 posterior to the opening of the cord. 



Variations in the Aortic Arches and the Origin of Arteries in 

 Reptiles. f — F. Hochstettor has observed and collected a large number 

 of cases which he arranges iu four groups: — (1) Cases in which the 

 obliteration of the ductus Botalli is partial or has not been effected, on 

 one side or on both sides ; (2) cases of supposed or real persistence of 

 a ductus caroticus (the region of the dorsal aortic root between the 

 openings of the third and fourth aortic arches), on one side or on both 

 sides ; (3) cases in which certain portions of the carotid system which 

 normally disappear are persistent ; (4) cases in which certain portions 

 of the aortic system which normally persist are obliterated. 



Development of Axial Skeleton in Amphibia.:}: — W. Kapelkin has 

 studied the embryos of various species of Triton, Salamandra, Ac, with 

 the special object of deciding some of the disputed questions in regard 

 to the number and origin of the sheaths of the notochord, and the part 

 played by its elements in forming the bodies of the vertebrae, together 

 with some other points. He finds that the central cells of the notochord 

 •early become vacuolated and degenerate, but the peripheral cells persist, 

 and form the so-called notochord epithelium, v\hich forms the thin noto- 

 chordal sheath on its outer surface. This sheath later splits into two, 

 the inner fibrous and the outer elastic sheath (clastica externa). Mean- 



* Bull. Johns Hopkins IIosp., xii. (1001) pp. 102-8 (2 pis. and 19 fi<js.). 

 + Morph. Jalirb., xxix. < IDul) pp. 415-38 (1 pi.). 

 : J Bull. Soc. Imp. Nut. Mosoou, 1900 (published 1901) pp. 433-48 (2 pis.). 



