ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 189 



number of rays, and the number of madreporic plates. The shape of 

 the disc is in general pentagonal, but tends to become circular in more 

 fully developed, individuals. Over ,75 p.c. had a coloured patch, which 

 varied in shape with its size — from circular to pentagonal. In the first 

 thousand specimens there were five with six rays ; in the second thousand 

 there were four with six rays, and one with four rays ; in the third 

 thousand there were three with six rays. Out of 3000 specimens, thirty- 

 nine had two or'more of the plates so like the madreporite, that one could 

 not tell the real madreporic plate — a confirmation of what Prof. Jeffrey 

 Bell says, that " in ophiurods the stone-canal ends in one or several 

 of the mouth shields." The paper affords a good illustration of the 

 variability of a familiar animal. 



Coelentsra. 



Medusa from Victoria Nyanza.* — Ch. Gravier calls attention to 

 Ch. Alluaud's discovery of a freshwater medusa in this lake. It seems 

 to be identical with Limnocnida tanganyim, discovered in Lake Tangan- 

 yika by Bohm in 1883, and studied in 1893 by R. T. Gunther — a relict 

 of the fauna of the ancient Jurassic sea which once covered the centre 

 of Africa. 



Sagartia paguri Verril.f — J. Play fair McMurrich describes this 

 interesting sea-anemone, which adheres to the chela of the pagurid 

 Diogenes edwardsii (De Haan). It was previously described briefly by 

 Verrill in 18G0, but without any details of structural characters. These 

 are now supplied. The habits of this form suggests its reference to the 

 genus Adamsia, but the arrangement of the mesenteries clearly indicates 

 it as a member of the Sagartiinse, and it is to be assigned to the genus 

 Sagartia. 



Modification of Hydroid Colonies by (Movements in the Water.J 

 Madame S. Motz-Kossowska has made many observations and some 

 experiments which show that Plumularia obliqua, Aglaophenia myrio- 

 phyllum, Eudendrium ramosum, etc., are modified by the movements of 

 the surrounding water. Changes of thickening in the perisarc, increased 

 flexibility or rigidity, may be referred to direct environmental influence. 

 The mechanical action of contact with solid bodies is also discussed . 

 The perisarc of a, free stolon is much more delicate than that of the fixed 

 hydrorhiza, and the growth of the stolon is far more rapid than that of 

 the hydrorhiza. 



Alaskan Corymorpha-like Hydroid. § — S. F. Clarke calls attention 

 to a large coral-red Alaskan Hydroid, for which he previously created the 

 genus Rhizomma, which he now finds, however, to be a species either of 

 Lampra or Corymorpha. To settle this it will be necessary to find speci- 

 mens with well-preserved gonophores. He notes the unusual thickness 

 of the supporting lamella between the ectoderm and the endoderm. 



* Comptes Rendus, cxxxvii. (1903) pp. 867-9. 



t Proc. U.S. Nat. Mus., xxvi. (190;?) pp. 427-8 (2 figs.). 



% Comptes Rendus, cxxxvii. (1903) pp. 863-5. 



§ Proc. U.S. Nat. Mus., xxvi. (1903) pp. 953-8 (7 figs). 



