§172. 



THE ACEPHALA. 



189 



of this order, the mantle receives, moreover, numerous blood-vessels, or 

 ramified prolongations of the body of the animal.'^* 



These last are spherical or star-like, with Salpa 

 maxima, and dendritic with Salpa bicaudata ; 

 with these species they are not soluble in hydro- 

 chloric acid, and are therefore probably composed 

 of sUex. In the mantle of Botrytlus, there are, 

 in certain places, peculiar flexuous fibres running 

 in all directions. If these are treated with pot:issa 

 they will appear evidently composed of cellulose. 



Accirdins; to KuUiker, the structure of the man- 

 tle of Cynthia jiapillata is still more complicated. 

 Its middle layer is composed of longitudinal and 

 circular flexuous non-azotized fibres. Between 

 these lie granules, nuclei, crystals and cells ; these 

 cells are nucleated, and contain, sometimes pigment 

 granules, and sometimes daughter-cells which gives 

 them the appearance of those of cartilage. 



KitUiker was unable to determine the structure 

 of the third and external layer which is horny, for 

 he had at his disposal only alcoholic specimens 

 of this Cynthia. He saw however that it united 

 with the middle layer to form the spines which pro- 

 ject from the sui-face of tlie skin. 



In the mantle of Cynthia pomaria, the longitu- 

 dinal fibres predominate, and between them lie 

 C!-ystaLs, round pigment-ceUs, and other cells which 



are peculiar and filled with yellow corpuscles ; and 

 finally, a third variety arising from the transform- 

 ation of the pigment-cells, whose walls are gradu- 

 ally thickened and ultimately split up into fila- 

 ments, forming concentric layers around the ceU- 

 cavity. When subjected to potassa, these cell- 

 membranes are decomposed, like the principal 

 fibres, into an insoluble, non-azotized substance, 

 while all the other elements of the mantle entirely 

 disappear under the action of this agent. 



The researches of KoUiker and Luwi^ uj)- 

 on the mantle of the Tunicata, have been r-- 

 cently published in the Ann. d. Sc. Nat. V. 1S46. 

 p. 193, PI. V.-VII.* 



5 Blood-vessels are found in the mantle of vari- 

 ous Phallusiae ; they are spread out in a reticu- 

 lated manner, especially in the external layer. 

 See CuvieT, Mem. sur les Ascidies, &c., p. 15, PI. 

 III. fig. 1 (Phallusia mamillaTis) ; Sniisni/, 

 Mem. &c. p. 102, PI. IX. fig. 1. B. (Phallusia 

 sulcata) ; and Delle Chiaje, Descrizione e not>- 

 mia desrli animali invertebrati della Sicilia citeriore 

 Tom. III. 1841, p. 33, Tav. LXXXIV. fig. 2 (Phal- 

 lusia monachus). 



* [ § 172, note 4.] The presence of cellulose in 

 animal tissues is a fact of no inconsiderable import- 

 ance in animal and vegetable physiology. The 

 subject has recently received much attention from 

 Schacht (Muller\i Arch. 1851, p. 176), and his 

 conclusions are sufficiently interesting to be pre- 

 sented in full. 



" 1. In the mantle of the Ascidiae there is a 

 substance insoluble in caustic potass, but soluble in 

 sulphuric acid, which is turned to a beautiful blue 

 by iodine and sulphuric acid, and which therefore 

 consists entirely of cellulose. This substance con- 

 stitutes the interstitial substance of the cells ; in 

 the mantle of Phallusia it is homogeneous, but in 

 Cynthia it occurs for the most part in a fibrous 

 form. 



" 2. The mantle of the Ascidiae contains beside 

 this cellulose, another material which is soluble in 

 caustic potass, but insoluble in sulphuric acid, and 

 not colored blue by iodine and sulphuric acid, and 

 which consequently is not ceUuIose ; in the mantle 

 of Phallusia it is only sparingly present, but in 

 Cynthia and the new Chilian Ascidian, it is much 

 more abundant and alone constitutes the corneous 

 epidermis of their mantle. 



" 3. The membrane of the cells in the mantle of 

 Phallusia does not consist of cellulose, it is colored 

 brown by iodine and sulphuric acid ; it is soluble 

 in caustic potass, and behaves exactly like an ani- 

 mal membrane as do the nuclei and vessels. 



" 4. In the mantle of Phallusia, cells abound in 

 a homogeneous, interstitial substance composed of 

 cellulose ; it is only at the inner margin of the mantle 

 that fibres composed of cellulose, with nuclei among 

 them, make their appearance. In Cynthia, &c., 

 there are scarcely any traces of cells, while the 

 nuclei and cellulose fibres abound. 



" 5. A tessellated epithelium, containing no cellu- 



lose, covers the inner surface of the three Ascidiae 

 which I examined ; the outer surface of the man- 

 tle of Phallusia appears to have a similar epithe- 

 lium. 



" 6. There are two essential points of difference 

 between the modes in which cellulose occurs in the 

 Ascidiae and in the vegetable kingdom : 



" (1.) In Phallusia, the cellulose constitutes the 

 inter-cellular substance, but does not, as in plants 

 form an integral part of the cell-wall itself. 



" (2.) In Cynthia and other species, the cellulose 

 forms free fibres, a form in which it is never ob- 

 served in the vegetable kingdom. 



" 7. The substance of the mantle of the Ascidiae 

 is not disintegrated by boiling with caustic potass 

 and nitric acid, like the vegetable cellular tissue, 

 into its elementary parts ; there is in it none of the 

 inter-cellular substance universally present in veg- 

 etable tissues, and by which the cells are connected 

 but which inter-ceUular material is never composed 

 of cellulose, as it resists sulphuric acid, but is solu- 

 ble in caustic potass, as well as by maceration ; " 

 see loc. cit. p. 197, 198. This valuable paper is 

 accompanied with three colored plates representing 

 sections, &c., of the mantle-tissues, drawn by the 

 camera lucida. 



From this it is clear that this discovery of cellu- 

 lose in animals is very far from confounding the 

 animal and vegetable kingdoms, for whatever else 

 may be said, the previously established law that 

 the animal cell-membrane always contains nitrogen, 

 retains its force. 



See, also, the report of Payen on KoUiker and 

 Lowis^s paper, before the Institute, in the Compt. 

 Rend. 1846, XXII. p. 581. 



But see for some dissenting views on this subject, 

 Huxley (Quarterly Jour, of Microscop. Sc. No. 

 1, Oct. 18-32, p. 22). —Ed. 



