26 Mindeskrift for J. Steenstrup. XXV, 



the biggest one a length of 1215 fi, whereas a larva from a stomach of a rat taken one 

 day after the feeding measured 1248 ^, having thus evidently been still longer, as in 

 one day it will hardly be able to grow as long as that in the mucous membrane of 

 the stomach of the rat. On the whole, it is growing but very slowly during the first 

 days after the transmission to the alimentary canal of the rat, as will be referred to 

 later on. 



The shape is slender (fig. 32) tapering but slightly towards the front end and keep- 

 ing its width until the anal region where rather quickly it narrows into a conical tail. 

 The front end is similar to that of the fully developed worm as far as shape and 

 appearance is concerned (fig. 26). The tail often terminates in two pointed papillæ- 

 shaped projections the shape of which is varying much according to the different in- 

 dividuals. Sometimes three projections will be found of unequal size, while in other 

 cases it proves very difficult to make out whether two or three are present. A most 

 peculiar wing-shaped prominence may also be found in some cases, the edge of which 

 is serrated or fringed. 



The pharynx is relatively longer than that of the fully developed worm and the 

 Chitin-intima is comparatively thicker, a faet which will sometimes recall the Rhab- 

 ditidæ. As to the shape of the diameter I have not yet been able to make out 

 whether it is prismatic or not. Oesophagus at this stage of development has about 

 the same length as the intestine; frequently, however, it is somewhat shorter; during 

 the following period of development the oesophagus, however, grows more quickly than 

 the intestine, as the front half of the animal increases considerably in length, being at a 

 certain point of time longer than the intestine. When later on the hind part of the 

 worm shows the greatest rate of growth the length of oesophagus comparatively 

 will decrease by and by. Even in the encysted larva the oesophagus has the shape 

 of the fully developed worm, the front part being slender, passing with a rather 

 sudden dilatation into the thicker proximal half. The nerve-ring shows itself very 

 distinctly and half way from the latter to the limit beetwen the thinner and thicker part 

 of the oesophagus the porus excretorius is situated (figs. 28 and 32). The genital rudi- 

 ment appears as a small egg-shaped body far back in the animal, nearly on the spot 

 where the vulva will be found later on. Even at this stage of development it seems 

 to consist of a number of cells, or at any rate of a syncytium with several nuclei. 



When feeding the rat on cockroaches containing encysted larvæ these will be found 

 to have entered into the mucous membrane of the stomach already the next day. As 

 above mentioned they may not only be observed here; not seldom they are found 

 in the mucous membrane of the oesophagus or of the tongue, so that it may 

 be supposed that the larvæ already are freed from the capsules while in the 

 mouth of the rat, owing perhaps to a purely mechanical influence during the chewing. 



