ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 585 



on a stone. The author discusses the relation of Selaginopsis to 

 Thuiaria. Varieties of Thuiaria link on to Selaginopsis, and colonies 

 of Selaginopsis pass through a Thuiaria stage. It seems likely that 

 Thuiaria is the older and better established genus from which the other 

 has diverged. 



Hydroids of the Scottish Antarctic Expedition.* — James Ritchie 

 communicates a supplementary report on these. The ' Scotia ' collection 

 includes 59 distinct species, but few of these were obtained in truly 

 Antarctic latitudes. Within latitudes higher than the extreme limit of 

 floating ice, 9 species were obtained. The total number as yet recorded 

 in the Antarctic circumpolar seas is 68, of which 36 must, so far, be 

 regarded as peculiar. As regards number of individuals the area is 

 thinly populated. The report includes a useful note on Myriothela 

 aiistro-georgide Jaderholm. Two species, Thyroscyphus tridentatus Bale 

 and Plumularia lagenifera Torrey, hitherto recorded only from the 

 South and North Pacific respectively, have been found in the South 

 Atlantic, and the ranges of several other species have been considerably 

 extended. Of new forms there are described the trophosome and 

 gonangium of Sertularia heterodonta from off Brazil, the trophosomes of 

 Antenella quadriaurita from G-ough Island, and of a variety of Lafoea 

 gracillima from deep water to the south of the South Orkneys. The 

 gonangia of Sertidaria rathhuni and Antennopsis scotise are described 

 for the first time. 



Hydroids from Andaman Islands.! — J. Ritchie describes a few 

 additions to the little known deep-water hydroid fauna of Indian Seas, — 

 Hebella crateroides, Diphasia thornelyi, Aglaophenia septula, Lytocarpus 

 annandalei, all new species. 



Porifera. 



New Fresh-water Sponge.J — N. Annandale describes Tubella 

 vesparioides sp. n., from Burma. It is closely related to T. vesparium 

 (Martens), from Borneo, differing from this species in its smooth, 

 amphioxous skeleton spicule, and in the deeply indented rotule of its 

 gemmule spicule. 



Protozoa. 



Optical Properties of Contractile Elements in Heliozoa.§ — Doris 

 L. MacKinnon points out that on the well-known theory of Engelmann, 

 contraction is dependent upon the presence of doubly refracting particles 

 (inotagmata). Engelmann claimed that all elements which contract in 

 one definite direction are doublv refracting. Along Avith F. Vies, 

 MacKinnon has shown that the cilia of the gills of the muscle are not 

 really doubly refractive, and that their apparent double refraction is 

 simply due to the depolarisation of light by refraction and reflection. 



* Trans. Rov. Soc. Edinburgh, xlvii. (1909) pp. 65-101 (11 figs.). 



t Ann. Nat." Hist., iii. (1909) pp. 524-8. 



% Records Indian Museum, ii. (1908) pp. 157 L 8. 



§ Journ. Physiol., xxviii. (1909) pp. 254-8. 



