Mr. G. W. Bailey on Siliceous Spicule in Actinise. 39 



search were likely to be entangled. On subjecting tbem to a mi- 

 croscopic observation I detected a number of very interesting and 

 beautiful forms, although the season was not the most favourable. 

 The first objects that attracted my attention were great numbers 

 of siliceous spiculse, precisely similar to those found fossil in the 

 infusorial strata above referred to ; these I found among the algse, 

 and also more abundantly in the mud of the docks. These spi- 

 culse resemble those found in some species of Spongia and Tethya, 

 and I believe that Ehrenberg refers the fossil ones to these genera ; 

 but an observation which I made leads me to suspect that some 

 of them, at least, are derived from the exterior rays of Actinia, 

 On examining with a high magnifying power the rays of a large 

 species of Actinia which had an orange-coloured base and olive 

 rays [A. marginata, Lesueur ?), I found that the white rays which 

 form the exterior circle appeared to differ from all others, being 

 filled with spiculse arranged with great regularity and in count- 

 less numbers, radiating from the axis of each arm (see fig. 1, h and 

 c). Each of the spiculse was perforated with a longitudinal cavity, 

 from which was protruded a very long and delicate fibre (see fig. 

 1, a). These spiculse resembled so much in their form, perfora- 

 tion, and general appearance, some of the fossil siliceous spiculse 

 above referred to, that, like the fossil ones, they must be sihceous. 

 This question I had not the means of deciding, but I hope it will be 

 settled by some of the Boston naturalists. 

 It is only necessary to burn one of the rays 

 and examine the ashes j the siliceous spi- 

 culse will of course retain their form after 

 ignition. It would be an interesting fact, 

 if, by means of these spiculse, we could 

 obtain evidence of the existence of species Of 

 of Actinia during the epoch of Eocene ter- 

 tiary ; for who would expect that such soft 

 and perishable creatures could leave, for 

 such a length of time, any trace of their 

 existence ? 



The annexed sketches were made merely 

 as memoranda, as I hoped to have further 

 opportunities for observation. They will 

 serve to indicate the form and position of 

 the spiculse, although they have no pretensions to accuracy. 



EXPLANATION OF FIGURES. 



a One of the spiculce from a white external ray of Actinia marginata ? 

 showing its longitudinal perforation and the long projecting filament, much 

 magnified. 



h Ideal longitudinal section of a ray to show the manner in which the 

 spiculse are arranged ; at d are seen the vibrillte, and at e the long filaments. 



c Ideal cross section of the ray. 



