ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 495 



The axis skeleton is surrounded by an epithelium of elongated 

 secreting cells, and in places there are desmocjtes or holding-cells — 

 shorter and wider than the othei's, and showing striations at the axial 

 end. These cells become connected with the mesogloea secondarily. 

 They may become isolated as the result of being completely enveloped in 

 horny material produced by the secreting cells. Desmocytes have been 

 previously described in Heliopora and in Madreporarians. " The evidence 

 in Pseudoplexaura is in favour of the view that the axis has an ecto- 

 dermic origin. 



Porifera. 



Sponges of Lake of Tiberias.* — Nelson Annandale proposes to 

 divide the Spongillida^ into two sub-families — the Spongillinge, in 

 which microscleres are present, and the Potamolepidin^, in which they 

 are apparently not produced. Of the five species found in the Lake 

 of Tiberias, one is a race {sijriaca Topsent) of the widely distributed 

 Ephydatia fluviatilis, and belongs to the Spongillin^ ; the four species 

 of Potamolepidinas fall into two genera, both of which are described as 

 new — Cortispongilla, with one species, 0. barroisi (Topsent), and Nudo- 

 spom/illa, with three new species. 



There is evidence that the sponges of the lake (which have Asiatic 

 rather than European or African affinities) have lost or are losing the 

 power of reproducing by gemmules. In other respects Gortispongilla 

 is a highly-specialized genus, remarkable for the production of a 

 skeletal cortex, due to the thickening or concentration of the transverse 

 spicule-fibres a short distance beneath the dermal membrane, and for 

 the development of a well-defined and almost symmetrical central 

 cavity that opens directly through the osculum. The resemblances 

 that exist between this genus and certain sponges of the genus Veluspa 

 (LubomirsJcia) from Lake Baikal are probably due to conversrence. 

 The species of Nudospongilla in the lake have well-marked stru'ctural 

 peculiarities, probably of an adaptive nature, but the characters of the 

 genus itself are rather negative, especially as regards its distinction from 

 Stratospongilla, a sub-genus of SpongiUa. 



^ Protozoa. 



Mitotic Division in Amoeba proteus.t— Lucy A. Carter describes the 

 process of division. When in an almost spherical condition and about 

 to divide, the amoeba puts out short blunt pseudopodia, very slowly, 

 all round its body, lengthens slightly, and, about fifteen minutes after 

 this first indication of lengthening, the final strand of protoplasm 

 snaps across and the two daughter-amoebse move away from each other. 

 Among the sections prepared, one case of mitotic division was seen. 

 The spindle appears to be multiple in character, imperfectly divided 

 into a number of constituent spindles, each one with its axis parallel to 

 the long axis of the nucleus. Tliese elementary spindles are arranged 

 side by side to the number of four or five. The equatorial plate is 



* .Journ. Prcc. Asiatic Soc. Bengal, ix. (1913) pp. 57-88 (4 pis.), 

 t Journ. R. Phys. Soc. Edinburgh, xix. (1913) pp. 54-9 (4 figs.). 



