532 MB. A, E. SHIPLBT ON SOME [Juue 19, 



3. AscARis TEANSFUGA. (Plate XXXV.) 



Numerous specimens taken from the stomach aud small 

 iutestiue of Ursus arctos, var. piscator. This seems to be the 

 commonest nematode pai-asitic in the intestine of Bears. Dujardin 

 (' Histoire Naturelle des Helminthes,' 1845, p. 158) describes speci- 

 mens from the alimentary canal of Ursus arctos aud Ursus maritimus, 

 and Linstow in his ' Compendium der Helminthologie," 1878, adds 

 Ursiis amerlcanus and U. labiattis to the lists of its hosts. Blan- 

 chard gives a short description of this species in the ' Annales des 

 Sciences Naturelles,' ser. 3, vol. ii., and a figure of the anatomy of 

 a male. 



4. ASCAEIS LTIMBBICOIDES. 



A single specimen from the small intestine of Smiia satyrus. 



Note on the Histology of Ascaris transfuga. 



The histology of Ascaris transfuga has not been described, and 

 although the structure of the animal departs in but few particulars 

 from that which obtains in the unusually monotonous group of 

 Nematodes, I have added a few notes on some of the more 

 interestiug features. 



The subcuticular layer of Nematodes has recently attracted a 

 good deal of attention ; in Ascaris transfuga it exhibits the usual 

 structure — that is, it is composed of numerous fine fibrils closely 

 matted together, with occasional nuclei scattered through the mass. 

 The nuclei are small and seem to be degenerating. This sub- 

 cuticular sheath surrounds the single layer of muscles, and is 

 heaped up along the venLral and dorsal middle lines and around 

 the lateral excretory canals ; it is most abundant in the latter 

 position, especially in the region of the midcUe of the body ; here 

 it shows signs of being divided into two halves by a line which 

 runs from the canal towards the cuticle (Plate XXXV. fig. ]), and 

 in longitudinal sections it often splits along this line. In this 

 region this tissue with the lateral canal may reach a quarter the 

 breadth of the body, but anteriorly and posteriorly the bands are 

 much more flattened. The dorsal and ventral accumulations of this 

 tissue are much less bulky, only a narrow membrane, compressed 

 between two contiguous muscles, passes from the subcuticular layer 

 and surrounds the dorsal and ventral nerves (fig. 1). 



Jammes ^ is of the opinion that this subcuticular layer forms 

 with the nerves a single tissue, whose basis is the ectodermic 

 neuro-epithehal element. He attributes the loss of the cellular 

 outline of the embryonic ectoderm to the direct influence of the 

 cuticle, \\hich is formed at a very early stage in the life of the 

 individual, and serves to protect the embryo from the action of 

 digestive juices of the host in which it lives. This explanation of 

 the early formation of the cuticle applies, however, only to the 



^ Anu. des Sci. Nat. vol. xiii. 1892, pp. 321-342. 



