LINGUATULID ARACHNID RAILLIETIELLA FURCOCERCA. 17 



body-rings very distinct acuminated papilla; are symmetrically 

 situated on the latero-ventral margin . The genital opening is on 

 the mid-ventral line on the first body-ring. The cuticle covering 

 the body is studded with small eminences which give it a rough 

 appearance, particularly evident on the large papilla;. The body- 

 wall being very fine and transparent, some anatomical characters 

 can be made out : — 



The intestine is straight and dorsal ; it receives the short 

 arcuate oesophagus slightly behind its anterior end, and opens 

 dorsally by the anal orifice, which is situated between the two 

 caudal appendages. The spermathecse are rounded and symme- 

 trically situated a little dorsally to the vagina, which opens 

 through the anterior genital pore. The uterus is an ample sac 

 which fills the whole body-cavity from the spermathecfB to the 

 caudal extremity and partly embraces the intestine. It is full of 

 eggs. On the internal surface of the body-wall the parietal 

 gland-cells can be seen arranged in small clusters or nests ; they 

 are situated in a more or less regular annular series, two or more 

 to each ring. The specimens described by Diesing evidently were 

 not mature, as appears from the double hooks. Moreover, many 

 of them were found not in the lungs, but in other organs of their 

 hosts ; they were therefore probably still migrating through the 

 tissues to the lungs. 



The hosts in which Natterer found the specimens described 

 by Diesing are not many, but they belong to diflerent orders ; 

 Diesing, in fact, gives three snakes : Coluber lichtensteini, C.Jlavi- 

 ventris, Boa constrictor, and a lizard, Avijjhisbcena flavescens. 

 As I have already observed in other papers dealing with this 

 group of parasites, the genus Raillietiella, difi'ering from all the 

 others of the family Linguatulidse, comprehends species of para- 

 sites coming from hosts of very difierent families : from Ophidia, 

 Lacertidae, and Ampliibia. 



According to Diesing li. furcocerca is to be found both in several 

 snakes and in a lizard of very peculiar habits, the AmpMshcena. 

 Although until now there is no direct evidence to the contrary, 

 I think it improbable that the same species should inhabit such 

 difierent hosts. For this reason I have thought it well to give 

 a more complete description of this parasite, so that comparison 

 may be made with specimens obtained from snakes. 



Although several species of Raillietiella have been described, 

 both in the adult and semi-adult forms, we have as yet no know- 

 ledge of the younger developmental forms, nor of the intermediary 

 hosts in which they Myq. Hitherto the majority of intermediary 

 hosts for those members of the family, at least, which are found 

 in snakes, have been mammals ; a large variety of mammalia 

 have often been found to act as intermediary hosts to the same 

 species of parasite. Armillifer amillatits, according to ISToc, has 

 been found at its larval stage in 36 species of mammals. Other 

 species, parasitic in crocodiles, have in all probability fish as their 

 intermediary host. It is probable that all these immature forms, 



Proc. Zool. Soc— 192y, No. II, 2 



