Prof. H. Karsten on Rhynchoprion penetrans. 307 



wide stigmata), and so closely that apparently neither air nor 

 fluid can find its way into them ; and, further, that in animals 

 which had lived for some time in the skin I could find no fine 

 tracheal ramifications of the ordinary spiral structure, whilst 

 these must at least have remained in connexion with the cloacal 

 stigma in case the want of access of air or the penetration of 

 fluid had induced the alteration of structure in the anterior 

 tracheae. 



In the animal in a free state, the alimentary canal shows the 

 same complicated structure as in the Pulices. Whilst parti- 

 cular sections of it exhibit a greater delicacy, a greater develop- 

 ment of the glandular appendages occurs; so that it would appear 

 that the chylification of the food is rather efl*ected chemically, 

 whilst in Pulex mechanical arrangements assist in the operation. 

 The latter applies especially to the nearly globular proventri- 

 culus, which, in Pulex irritans, is horny, folded, and internally 

 almost spinose, whilst in Rhynchoprion it is simply membranous, 

 and internally papillarly glandular. Similar papillar glands 

 occur in the large membranous true stomach of both species, 

 especially in the vicinity of the anterior orifice. Before the crop, 

 there is in Rhynchoprion a long muscular oesophagus, which 

 appears to assist the passage of the inhausted nourishment into 

 the stomach by powerful peristaltic movements ; for it is always 

 found constricted into a number of globular sections. At the 

 commencement of the oesophagus there are two tufts of cylin- 

 drical salivary glands, each inserted by a common eff'erent duct; 

 and instead of the small pedunculate pyriform glands, which in 

 Pulex open into the intestine, as Malpighian vessels, in the 

 vicinity of the pylorus, there are, in Rhynchoprion^ two very long 

 glandular tubes, which pour their contents by a common efferent 

 duct into a region of the intestine which I cannot exactly par- 

 ticularize, as I never succeeded in observing these organs in 

 connexion. 



Of all these organs forming the tractus intestinalis, I could not 

 with certainty detect anything in the dilated parasitic female — 

 or, at least, I could recognize nothing with certainty — as any 

 parts of the stomach and intestine that might have been pre- 

 sent were so much softened as to lose all connexion during 

 preparation. 



That the ova, which now alone fill the much-dilated abdomen, 

 and which have grown to an extraordinary size, are not, as stated 

 by all previous observers, hatched in the body of the parent, 

 is shown not only by the fact that fecundated ova are never 

 found in the parasite, but also by the period of fecundation neces- 

 sitated by the anatomical conditions. 



The large ova, which grow to about half the length of the 



20* 



