MOUNT ST. GOTHARD TUNNEL LABOURERS. 145 



ON THE DEVELOPMENT OF THE SO-CALLED ANGUILLULA INTES- 

 TINALIS OF BAVAY. 



The eggs of the so-called Anguillula intestinalis are more ovoidal, 

 less elliptic, that is, with the ends less acuminated, less obtuse ; 

 they have, however, very variable diameters, like those of the 

 Dochmius duodenalis. Their longitudinal diameter is between 50 

 and 58/x. and rarely reaches 60/x., the transversal between 30yu. and 

 34yu., rarely 36;u. 



The eggs scarcely emitted present themselves with the yolk 

 segmented in 2, 3, 4, 5, 6, even 8 cellules. Placed in incubation 

 in places adapted, and at a temperature of 25 to 26 deg. cent., 

 they are developed rapidly, though in an irregular manner. For 

 these also the rajDidity of the development essentially depends on 

 the degree of heat in which are maintained the substances of incu- 

 bation. After 12 to 16 hours of incubation, many eggs are found 

 with the embryo nearly or entirely developed, which rolls in diffe- 

 rent ways inside the Qgg^ and after 14, 16, to 20 hours, more or less, 

 numerous embryos will be found issued from the respective eggs. 

 These entirely developed embryos appear already through the shell 

 of the eggs with greater brightness than those of the Anchilostoma, 

 and have more rapid motion. They adapt themselves, like the 

 others, to the convexity of the sides of the eggshell, and reach a 

 length about four times that of the egg. The hatching is rapidly 

 accomplished, and usually by means of the head. Once, however, 

 I saw an embryo issue tail first from the egg ; the tail was straight 

 and without motion, because, with the hope of finding the larvae at 

 the moment of opening the egg, I examined the preparations at a 

 comparatively low temperature (10 to 12 deg. cent.). 



The embryo is usually torpid for a short time after first issuing 

 from the egg, but not always. Soon afterwards the larva moves in 

 different directions, with a rapid, serpent-like motion, particularly if 

 the preparation be maintained at a proper heat. The larvae, as soon 

 as born, have a length of 200 to 240yu., a transversal diameter of 

 12^. ; are slender anteriorly, and terminate with a very sharp tail, 

 so that it is difficult to distinguish them from the larv^ of the 

 Anchilostoma. They have also an apparently three-lobed head, a 

 rectangular mouth-like cavity, which iscontained in a first swelling 

 of the pharynx, which becomes restricted, to constitute afterwards 

 an inferior swelling or pharyngeal bulb. The intestine is also cellular, 



