ZOOLOGY AND BOTANY, MICROSCOPY, ETC. G37 



of a mass of naked sarcode, without differentiation at the periphery 

 into a membrane or other tegumentary layer of any kind. On the 

 one hand, Steiu and Fraipont consider all Acinetidse without excep- 

 tion to be provided with an integument ; whilst Cienkowski and 

 Hertwig affirm tbat tbey have vainly sought for any integument in 

 Podophrya fixa, whose body is naked. After examining the arguments 

 of either side, the author states his own adherence to the view of the 

 latter, what he has himself observed in Sphcerophrya magna, still 

 further supporting it. The periphery of this species is siniply 

 bounded by a thin cortical zone of hyaline sarcode, not distinct from 

 the medullary sarcode, and showing none of the differentiations 

 proper to the true membranes with double outline. The existence of 

 Acinetidae completely destitute of all covering membrane must, there- 

 fore be considered a well-established fact. 



With regard to their integument the Acinetidae being unicellular 

 organisms, we must accept as a cell-membrane any peripheral layer 

 with a double outline, which may exist closely applied to the surface 

 of the body, and the author, after a long retrospective discussion of 

 the views hitherto held (by Stein, Claparede and Lachmann, Hertwig, 

 and Fraipont), states his own views. The Hemiophrya and Podo- 

 phrya are provided with a single tegumentary covering which corre- 

 sponds morphologically to a cell-membrane. The integument of 

 Dendrocometes, Dendrosoma, Ophryodendron, and Irychophrya has 

 the same value. The capsule, in which Acineta and Solenophrya 

 are lodged, cannot, on the contrary, be compared to a cellular mem- 

 brane, but is only a skeletal structure having no homology with the 

 integument of the other genera. The existence of a second membrane 

 within the shell, and applied to the surface of the body of the Acineto3, 

 has not been definitively shown in any species of this genus, and he 

 is able positively to deny its presence in those which he has studied. 



The existence among certain Acinetidas of two sorts of tentacles, 

 one destined for seizing prey, and the other for its suction, is a well- 

 ascertained fact which requires no further support. Although differ- 

 entiated in their functions, the two kinds have, however, the same 

 morphological value, and are evidently derived from the same primitive 

 organ. Fraipont has given excellent reasons in support of this view, 

 and to these the author further adds the fact that in Hemiophrya 

 gemmipara both kinds of tentacles penetrate into the body, whilst in 

 Hemiophrya microsoma, the sucking tentacles alone have this internal 

 prolongation. There is here a gradation in the differentiation and 

 specialization of structure, which added to other analogous facts men- 

 tioned by Fraipont, shows that these two distinct forms are derived 

 from one primitive form, which, in its structure and its relations with 

 the body, must be similar to that which exists in Podophrya and 

 Sphosrophrya. Fraipont calls this primitive organ a prehensile sucker, 

 wishing thus to point out its double function of absorbing and 

 seizing. 



Two very different opinions have been held as to the structure of 

 the tentacles. On the one hand Claparede and Lachmann define them 

 as " hollow tubes with contractile walls furnished with a sucker at 



Ser. 2.— Vol. It 2 X 



