282 RECORD OF CURRENT RESEARCHES RELATING TO 



the muscles of such animals as are without a nervous supply, while we 

 know this not to be the case. 



Whatever our opinions with regard to nomenclature may be, the 

 difficulty of explaining the manner in which the muscular layer of the 

 sponge receives its stimuli remains the same ; it is so important a 

 tissue of the sponge, so perfectly differentiated, that one can liardly 

 believe associated nerve-structures to be absent ; and yet no trace of 

 the presence of such structures has been discovered. The large ellip- 

 tical cells underlying the muscular layer and surrounding the sub- 

 cortical crypts are wonderfully like ganglionic cells ; but though they 

 sometimes are elongated in one or other direction into a tear-drop 

 shape, yet they are never prolonged into any distinct thread which 

 might be regarded as a nerve. They do not seem to be nerve-cells, 

 and perhaps they may be " ova" ; but without tracing their development 

 it is impossible to say. On the whole, Mr. Sollas is disposed to regard 

 them as the ordinary cells of the mark rendered very distinct by their 

 occurrence in a tissue of markedly contrasted character. The spicules 

 which extend beyond the surface of the sponge might perhaps suffice 

 to convey a mechanical stimulus to the muscular layer, though this 

 view is certainly attended with serious difficulties. 



Replacement of Siliceous Skeletons by Carbonate of Lime.*— 

 Mr. W. J. Sollas at the Sheffield meeting of the British Association 

 gave an account of certain calcareous fossil remains which exhibit, 

 both in gross and minute structure, a close resemblance to certain 

 existing siliceous sponges, and which differ widely from any known 

 form of calcareous sponge. The natural inference appears to be that 

 the calcareous fossils were once siliceous sponges, the siliceous parts 

 of which had undergone replacement by carbonate of lime. The 

 alternative view that the fossils were originally calcareous, and that 

 they represent an extinct group of Calcispongia, presents far greater 

 difficulties to the zoologist than the inferred mineral replacement 

 offers to the chemist. Siliceous sponge spicules are remarkably 

 soluble, yielding readily to the attacks of minute boring alga), and 

 undergoing solution in sea-water soon after the death of the sponge 

 which possessed them. 



The Eadiolaria of the carboniferous limestone the author regards 

 as having once possessed a siliceous composition, which they have 

 since exchanged for a calcareous one. 



Protozoa. 

 New Infusoriat (Plates VII. and VIII.|).— Dr. August Gruber now 

 describes in detail the new species of Infusoria of which he previously 



* ' Eep. Brit. Assoc. Adv. Sci.,' 1879, p. 350. 

 t 'Zeitsch. wiss. Zool.,' xxxiii. (1879) p. 439. 



X EXPLANATION OF PLATES VII. AND VIII. 



Fig. 1. — Stichotricha socialis. A medium-sized colony, x 90. The tubes are 

 shown partly in optical section, partly in surface view. The colony occurred 

 hanging downwards from the surface of the water. 



Fig. 2. — Ditto. The animal from the ventral side. W, the first large cilia of 

 the peristome ; m, the so-called undulating membrane, rf-presentcd as a thin line, 



