INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 799 



The fourth chapter of this very valuable essay deals with the 

 development of the Chastognatha, for the study of which S. hipunctata 

 and S. serratodentata are reported to be very suitable objects. Here 

 we can only very briefly note one or two points. (I) There is formed 

 a typical gastrula. (2) Before this stage is lost, part of the endoblast 

 gives rise to the fii-st elements of the generative organs, and another 

 part to the rudiments of the enteric canal and of the body-cavity. 

 (3) The two large cells in the endoblast of the gastrula give rise to 

 the male and female generative organs. For the further consideration 

 of these and other points our space compels us to refer to the figures 

 and descriptions given in the original. 



Disease produced by Anchylostoma duodenalis.* — The develop- 

 ment of this parasite has been followed by Professor Perroncito up to 

 the stage at which it enters the body of man, and is of especial im- 

 portance with regard to the epidemic caused by it among the work- 

 men at the St. Gothard tunnel. Three parasites occur in the 

 intestine, all producing the same symptoms, and causing the disease 

 known as Oligcemia perniciosa ; they are Anchylostoma (Dochnius) 

 duodenalis, Anguillula intestinalis and stercoralis, and may occur in the 

 different subjects either separately or mixed. 



Larval development of Ancliylostoma duodenalis outside the human 

 body. — The eggs are oval, thin shelled, transparent, measuring • 052 

 by • 032 mm. At twelve to fourteen hoiu's from the commencement of 

 incubation, traces of larvae are visible in a very few ; in one to two days 

 most show larvas in various stages, and after some days they issue. In 

 eggs kept at between 28^ and 33° C. the exit is seen to be made by two 

 or three blows which occur within a minute of each other ; the head 

 emerges generally a little to the side of one of the poles ; the first 

 effort is the most vigorous, for it springs out, moving the body 

 laterally with great force ; the movements continue for a short time, 

 and then a period of quiescence and expansion ensues ; the length at 

 birth is ■ 2 mm. and maximum diameter • Oli mm. ; the body is 

 slightly attenuated in front of the pharynx, and ends posteriorly in 

 an awl-like thin tail ; the head is trilobate, and a rectangular tube 

 •014 mm. long represents the mouth; the pharynx has an anterior 

 dilatation, and a little behind tliis, another, the pharyngeal bulb, 

 carrying chitinous teeth; the whole tube is strongly muscular and 

 leads into an intestine with a zigzag cavity, ending at a slightly 

 prominent anus. The rudiment of the genital apparatus is seen as an 

 oval mass near the middle of the body, on the anal side, between the 

 intestine and the dermal muscular layer. After the first day the 

 larva is • 25 mm. long, and continues to increase at the rate of • 05 mm. 

 per diem, as long as the. temperature docs not exceed 21*^ to 25^ C. ; 

 the maximum length is "55 mm., the breadth -02- -02-1 mm. After 

 eight hours of life, the intestine assumes a straight position. After 

 some days, serpentine movements occur at temperatures even of l-i^ 

 to 10'' C. After the maximum size is attained, the pharynx under- 

 goes modifications, and is finally altogether renewed. Moauwhilo, 



• ' Atli Acciul. Lincei (TmiiBUuti),* iv. (1880) p. 179. 



