PHYSIOLOGY OF SPONGES. 317 



p. 387) observed in India that Spongilla ceases its currents during the hot 

 hours of the day, the oscula aud pores remaining open ; he deduces that the 

 flagellar motion must have ce;ised. My experiments on the currents of 

 Calcaronea at Naples do not show this, but the records show some evidence 

 of a possible reduction in power in the hottest hours. But, for the question 

 before us, a rise in temperature sufficient to paralyse the flagella of the collar- 

 cells might be expected also to suspend the movements of the spermatozoa, 

 so that entrance by the osculum would not then be effected. 



I cannot find any satisfactory record of an observation showing with 

 certainty that in a sponge, with its apertures open and its collar-cells 

 unchanged, motion of the flagella spontaneously stops and begins again. 



Such is certainly the impression gained on first experiments with living- 

 sponges ; but as experience makes allowance for injury, temperature, 

 suffocation, obstruction by air-bubbles, etc., the impression steadily 

 diminishes. The result of rather prolonged work on the living collar-cells 

 (1895) was to make me regard a motionless flagellum as a sign of death, or 

 danger of death, in the cell which bore it. 



Note C. — On Odour and Excretory Granules (p. 299). 



In regard to the stronger and more pleasant odour possessed by Clathrinida? 

 as compared with Sycon, Grantia, etc., I am pleased to be corroborated by 

 my friend, Mr. L. R. Crawshay, who very kindly made observations on the 

 shore at Plymouth, collecting Clathrina coriacea and Sycon separately in 

 stoppered bottles. His experience accorded with my statement, though, the 

 season being mid-winter, the conditions were not very favourable. 



There is evidence of a direct character that considerable difference exists 

 between these two groups in the nature of the granules formed by the 

 porocytes and ectocytes. I found indigo-carmine deposited freely in the 

 ectocytnl and porocytal granules of Clathrina clathrus (1892 h), GuancJia 

 coriacea, and Ascaltis cerebrum and reticulum ; but never was able to 

 demonstrate deposit with Sycon raphanus, Leucandra aspera, or Grantia 

 compressa : and Cotte (1903, p. 159) also obtained negative results with 

 Sycon raphanus. The facts suggest a modification of my views as to excretion 

 (1892 b, compare Urban 1903 and Minchin 1908)*. That is to say, it 

 appears logically possible that these refractive lipoid granules, of which I 

 have recorded (I. c.) many puzzling reactions, are not in all sponges formed 

 by a process which also secretes sulphindigotate of soda; but that in the 

 Calcinea (and possibly at sexual times in Sycon) an odoriferous body is added 

 which is so formed. 



Gotte has a very interesting observation (/. c. p. 528), that the individuals 

 of Sycon raphanus, which were " exceptionellement riches en pigment jaune 



* See also footnote, p. 323, 

 LINN. JOURN. ZOOLOGY, VOL. XXXIV. 21 



