214 EDWARD VAN BENEDEN. 



column producing the effect of lighter longitudinal stria- 

 tions. The channelings and the longitudinal striations that 

 are their consequence appear and disappear, and it is im- 

 possible for one to tell the signification of this arrangement. 



Many naturalists have described the longitudinal striation 

 of the body of certain Gregarinse. Lieberktihn ^ recognised 

 such a striation at the posterior extremity of the body of 

 Gregarinse that are found in the testicles of Lumbrici (' Mono- 

 cystis et Zygocystis' of Stein). Just as Claparede/ who 

 observed a double system of striations on the surface of the 

 body of a Gregarina, from a Phyllodoce, so Lieberkiihn has 

 neither inquired the cause nor the signification of these 

 striations. Leidy^ first described a layer distinctly charac- 

 terised by longitudinal striation, and called it the muscular 

 coating (it corresponds to our cortical coating). Leuckart* 

 confirms the observations of Leidy, but he emits the 

 opinion that the striation depends on the momentary 

 folding of the subcuticular cortical membrane. This per- 

 fectly correct interpretation has been recently adopted by 

 Ray Lankester.-'^ According to him, also, the longitudinal 

 striations are only the result of a state of momentary contrac- 

 tion of the would-be muscular tunic of Leidy. When I 

 published my first work on the Gregarinae of the lobster, 

 I then also recognised the true value of the longitudinal 

 striations, attributing them, not to an organic permanent 

 disposition, but to a passing state of the cortical tunic of 

 Leidy. ^ Nothing, however, proves the muscular nature of 

 this coating ; the longitudinal striations are not muscular 

 longitudinal fibrils, but the result of a thickening, following 

 a longitudinal direction, of the cortical substance. This is 

 probably susceptible of local contractions ; it is likely that 

 it allows the Gregarine to roughly bend, in elbow form, and 

 also determines the movements of translation of the granules 

 of the medullary fluid layer ; but it consists only of proto- 

 plasm, not transformed into muscular substance. 



A third very thin coating, which has completely escaped 

 the observation of naturalists who have studied Gregarinse, 



1 Lieberkiihn, ' Evolutions of the Gregariues,' p. 24, pi. i, fig. 1. 



2 Claparede, ' Anatomical Investigations among the Hebrides,' p. 43, 

 pi. V. 



^ ' Transactions Amer. Phil. See. at Philadelphia,' 1855, vol. x. 



■» Leuckart, 'Bericht iiber die Leistungen in der Naturgeschichte dor 

 niederen Thiere walirend der Jahre,' 1841 — 1853, p. 108. 



* Ray Lankester, 'Transactions Micro. Soc.,' 1, VI, pp. 23-28, Tab. V. 



^ Edouard van Beneden, " Sur une uouvelle espece de Gregarines 

 designee sous de uom de Gregariues," ' Bull, de I'Acad. Roy. de Belg.,' 2 

 serie, t. xxviii, p. 447. ' Quart. Journ. Micro. Science,' vol. ix, new ser. 



