ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 751 



we do know is that a body whicli is at obg time visible becomes invisible 

 by repeated divisions, but we recognize that it is still present. 



Tbe chief multinuclear holotrichous Infusoria are HolopJirya ohlonga, 

 Lagynus elongatus, Chcenia teres, Trachelocerca phoenicopterus, and T. minor 

 (sj*. n.) ; while the hypotricbous are Holosticha lacazei, multinucleata, 

 Jlava, scutellum, Uroleptus roscovianiis, zignis, Epiclinites auricularis, 

 vermis (sp. n.), and Gonostomum pedicidiforme. 



Researches on Ciliated Infusoria.* — M. Fabre-Domergue divides 

 his present memoir on the ciliated Infusoria into a descriptive and a 

 general part. The former is necessary on account of the disorder and 

 confusion which obtains in our knowledge of the holotrichous forms, on 

 which we have not such fine monographs as those of Stein on the other 

 groups. The species dealt with are Frorodon niveus, Cyrtostomum leucas, 

 Ophryoglena atra and 0. flava of Ehrenberg, Flagyopyla fusca of 

 Quennerstedt, Balantiditun elongatum of Stein, and Monodinium Balhianii 

 g. et sp. nov. The last differs from Didinium nasutum by having only 

 one anterior circlet of cilia in the adult stage, and two in that of division, 

 and by its smaller size. From Mesodiniiim it differs in the character of 

 its cilia. 



In the general part the author commences with an account of the 

 protoplasm ; this is made up of two elements which are closely united — 

 a solid reticulated hyaloplasm and a liquid paraplasm. Both these 

 elements are endowed with a very high degree of osmotic power, but 

 they cannot mix with water during life. It is on the hyaloplasm that 

 the density of the protoplasm dej)ends ; it is contractile, and is capable 

 of fusing with itself ; it is in its mass that true nutrition is effected, and 

 in it that reserve or excreted material is deposited ; it is eminently 

 coagulable by acids, heat, &c. When fresh it is soluble in potash, but 

 cannot be attacked by that reagent after it has been coagulated. 



The paraplasm corresponds to the sarcode of Dujardin, as he studied 

 it by transudation through the cuticle of Paramsecia. Its chemical 

 properties ai-e the same as those of hyaloplasm, but it has no contractility. 

 The ectoplasm is a more or less dense layer of hyaloplasm ; in some cases 

 the reticulations of the endoplasm are closely packed, when it is dense 

 and exhibits no cyclosis, which, however, may be seen when the reticula- 

 tion is loose. The endoplasm sometimes presents a disposition to form 

 a digestive tube without proper walls ; the most marked differentiation is 

 met with in Didinium nasutum and Monodinium Balhianii. The con- 

 tractile system is exclusively situated in the innermost layer of 

 ectoplasm ; it may be localized at one point of the body in the form of a 

 simple vesicle, with or without a differentiated peripheral layer, or it 

 may form a plexus which completely surrounds the body of the Infusoria. 

 The contractile vesicle opens to the exterior by one or several pores, 

 which, in species with a thick ectoplasm, always remain open, and are 

 only closed by a layer of contractile hyaloplasm. This last may be 

 differentiated to give rise to the contractile fibres of Vorticella, Stentor, or 

 other contractile forms. There seems to be a relation between the 

 muscular differentiation and that of the layer of trichocysts, the one 

 excluding the other. The ectoplasm corresponding to the cortical layer 

 may give rise to a secretion layer, the presence of which is more or less 

 constant, and which may be considered as the homologue of the cuticle. 



* Ann. Sci. Nat., v. (1888) pp. 1-140 (5 pis.). 



