452 SUMMARY OF CURRENT RESEARCHES RELATING TO 



occurs. The phenomenon of association in general is discussed, the 

 conclusion arrived at being that it is not a primitive but an acquired 

 condition. The power of cy to tactic attraction has become so developed 

 and specialised in Gregarines, that it is now most probably necessary 

 before sporulation can take place. 



Castration due to G-reg'arines.* — Gr. Smith gives some notes on the 

 life-history of Aggregata inachi sp. n. No trace of conjugation prior to 

 encystment, nor of two nuclei together in one cyst, was found. Amongst 

 the sporozoites found free in the body of the crab a tendency to form 

 associations was noted. The presence of the parasite in the male Inachus 

 is associated with the occurrence of external hermaphrodite characters 

 and with the disintegration of the testis, only the vesiculse seminales 

 remaining. The assumption of the hermaphrodite characters would 

 appear to take place at the moult following the liberation of the 

 sporozoites into the body cavity. 



Structure and Life-History of Pleistophora periplanetse.f — W. S. 

 Perrin gives some particulars regarding this Myxosporidian parasite of 

 Periplaneta orientalis. There are two very definite phases in the life- 

 history : a schizogonous phase, characterised by almost excessive multi- 

 plication, with a view to auto-infection ; and a sporogonous phase, 

 pharacterised by the cessation of growth and trophic activity, and the 

 formation of resting spores. This by no means agrees with Schaudinn's 

 division of the Sporozoa, where the Myxosporidia are placed in the 

 Neosporidia, in which spore-formation continues during the trophic phase. 

 Another point of interest in the life-history of Pleistophora periplaneta, 

 is afforded by the existence of residuary nuclei, which, together with the 

 protoplasm of the pansporoblast, die off, while sporulation is being 

 effected. The author regards it as possible that these residuary nuclei 

 represent reduction bodies. 



Spirochsete pallida and Syphilis .% — C. Thiesing adduces various 

 considerations which lead him to doubt whether this form is a3tiologi- 

 cally connected with syphilis, and whether it is a protozoon. He regards 

 it as a harmless saphrophyte, and as a plant, not an animal. 



* Mitth. Zool. Station Neapel, xvii. (1905) pp. 406-10 (1 pi.), 

 t Quart. Journ. Micr. Sci., No. 196 (1906) pp. 615-33 (2 pis.). 

 I SB. Ges. Nat. Freunde Berlin, 1905, pp. 205-17 (1 pi.). 



