520 SUMMARY OP CURRENT RESEARCHES RELATING TO 



(5) they are abundant in one time of the year and not at another ; 



(6) they are seen on the stage of the Microscope to penetrate and 

 enter cells by means of their active movement ; (7) they are also seen 

 to escape from cells by the same activity ; (8) they are localized 

 chiefly in the spleen though not confined to that organ ; and (9) though 

 most abundantly observed in certain specimens of Bana esculenta at 

 Leipzig, yet they have also been observed in Bana temporaria and in 

 Triton sp. 



These observations are not merely consistent with the view that 

 Drepanidium is an independent parasitic organism, but are directly in 

 favour of that view, since they are readily explained if that view be 

 admitted, whilst they remain as isolated and unconnected facts, each 

 requiring a special assumption for its connection with any other 

 theory which may be advanced as to their nature, when the obvious 

 one that they are parasitic organisms is rejected. 



The only fact which Dr. Gaule adduces which is inconsistent with 

 the parasitic nature of Drepanidium is that in some cells, especially 

 blood-corpuscles, these bodies are not present when an examination 

 of them is first made on the field of the Microscope, and that on the 

 addition to the preparation of 0*3 per cent, solution of sodium 

 chloride the Wurmchen are formed there and then in the cells. 

 Prof. Lankester, however, doubts altogether the accuracy of Dr. 

 Gaule's statements on this point, the supposed fact being really an 

 erroneous interpretation of an observation. Just as the nucleus in 

 the frog's red corpuscle is frequently not visible during life and only 

 becomes visible as the result of the first change in blood removed 

 from the blood-vessels, so Drepanidium is invisible in the normal 

 condition of the red blood-corpuscle owing to the identity of the 

 refractive index of its delicate substance and that of the body of the 

 corpuscle. It only becomes visible when a change in the refractive 

 indices takes place. 



Prof. Lankester suggests that researches should be directed to the 

 discovery of a Gregariniform stage, and of cysts containing spores, or 

 of isolated spores in which several Drepanidia may be enclosed. 

 These phases in its life-history are very possibly to be met with 

 in other regions of the frog's body than the blood-vessels or the 

 spleen. 



Development of Trypanosoma.* — Dr. J. Gaule has also re- 

 investigated the remarkable organism of Flagellate character found in 

 frogs' blood, the so-called Trypanosoma sanguinis Gruby, and puts 

 forward a decidedly new and original interpretation of it, arriving at 

 the conclusion that it is not an independent organism, but is produced 

 by spontaneous modification of the white blood-corpuscles. Its pro- 

 duction is favoured in general by warmth, hence it is found in frogs 

 more particularly at the commencement of the warm period of the 

 year, and it may also be seen to occur during the winter in frogs 

 which have been kept in a warm room. These conclusions are 

 attempted to be supported by the fact that the direct and frequent 



* Arch. Auat. u. Physiol., 1880 (Physiol. Abth.) pp. 375-92 (1 pi.). 



