On FrenzeVs Mesozoon Salinella. 465 



LXVIII. — Criticdl Ohsprvatlons on FrenzeVs Mesozoon Sali- 

 nella : a Biological Sh.tch. By Prof. Stefan ArATiiY*. 



In the ' Zoologischer Anzeigcr ' for 1891, no. 3G7, pp.230 

 et seq.'\, and in the ' Biolofi^isches Central blatt,' Bd. xi. 

 pp. 577 et seq.\j Frcnzel described a new animal, on which 

 he bestowed the name Salinella §. The creature is a tube 

 provided with two apertures — mouth and anus — and its wall 

 consists of a SINGLE LAYER OF CELLS. The cells on the 

 ventral surface are similar to one another and finely ciliate ; 

 it is only around the mouth, which is not quite terminal in 

 position, that certain of the cells are provided with stouter 

 cilia. On the dorsal side the cells bear short setae instead of 

 cilia. The surface of all the cells which is turned towards 

 the intestinal cavity is likewise finely ciliate. Food-particles 

 are found in the intestine in a solid form. Frenzel is led to 

 believe that intracellular digestion does not take place. 



By the discovery of Salinella our store of facts received a 

 very material addition, since the creature in question, as it 

 appears to me, serves to a certain extent to fill the ga]) 

 between Volvox and Trichopla.v. For the comprehension of 

 the most primary forms of multicellular life Salinella seems 

 more important than the Orthonectids and Dicyemids, in 

 which we find a genealogical stage, certainly a very ancient 

 one, at the best merely restored by parasitism as a fully- 

 developed animal. 



A large number of questions of the highest biological 

 importance can be connected with Salinella ; but although in 

 Salinella Frenzel furnishes an important contribution for our 

 comparisons, he himself, in criticizing it and the problems 

 connected with it, does not make sufficient use, for the pur- 

 poses of comparison, of the store of facts already available. 

 The result is that certain difficulties, which are indeed present, 



* Translated from the ' Biologisches Centralblatt,' xii. Bd., no. 4 (Feb. 

 29, 1892), pp. 108-123. 



t Ann. & Mag. Nat. Hist. ser. 6, no. 49, Jan. 1892, pp. 109-111, "A 

 Multicellular Infusorian-like Animal." 



X Ann. & Mag. Nat. Hist. loc. cit. pp. 79-84, " The Mesozoon Salinella."' 



§ Under the title " Untersuchungen iiber die mikroskopische Fauna 

 Argentinians," Frenzel publishes a detailed description, with figures, in 

 the last part of the ' Archiv fiir Naturgeschichte ' (58 Jahrg., i. Bd., 

 1 Heft, pp. 66-96, Taf. vii.). This was issued last December, but it did 

 not come into my hands until later. In this paper Frenzel adds to his 

 previous statements nothing that is essentially new ; I therefore consider 

 it unnecessary to discuss it further at present. 



Ann. & Mag. N. Hist. Ser. 6. Vol. ix. 35 



