342 Mr. J. W. Fewkes on a Method of 
mens and preparations and valuable assistance and advice; my 
thanks are also due to Dr. Albert Giinther, F.R.S., for kind 
permission to refer to the British Museum Collection, as well 
as to Mr. R. Kirkpatrick, in charge of the sponges therein, 
for ready and effectual assistance in doing so. 
EXPLANATION OF PLATE XVI. 
A. Microciona strepsitoxa. 
Figs. 1 & 2. Main skeletal spicules. 
Fig. 3. Echinating spicule. 
Fg. 4. Subclavate style. 
Figs. 5 & 6. Long toxites. 
Fig. 7. Smaller form of toxite. 
Fig. 8. Long toxites; from a photograph, to show central twist. 
Figs. 9 & 10. Isochele, front and side views. 
[Figs. 1-7 magnified 260 diameters; figs. 9 & 10 magnified 
850 diameters. | 
B. Trachytedania (?) echinata. 
Fig. 1. Main skeletal spicule. 
Fug. 2. Echinating spicule. 
Fg. 3. Tylote spicule. 
[ Figs. 1-8 magnified 260 diameters. | 
XLIV.—On a Method of Defence among certain Meduse. 
By J. WaAurer Frewkes*. 
THE Siphonophora, in common with other Medusee, as is well 
known, possess a very powerful organ of defence in the sting- 
ing-cells, also called lasso-cells and nematocysts. There is 
reason to believe that there may be at least one other method of 
protection adopted by these animals. I propose this evening 
to lay before you the evidence of the existence of this second 
method of defence made use of by these animals, and to open 
the discussion of the homologies of the structures in which 
this new means of protection is lodged. 
It may be well to anticipate what follows by the statement 
that the new method of defence is that of discolouring the 
water by the emission of coloured pigment from certain chro- 
matic cells on the bracts, and that these cells bear relation- 
ships and perhaps are homologous with the nematocysts in 
* From the Proce. Bost. Soc. Nat. Hist. vol. xxiy. pp. 200-208. 
