Mr. H.J. Carter on the Development of the Sponge-spicule. 429 



The same kind of bodies which Dr. Th. Eimer found in the 

 siliceous and calcareous sponges at Capri, from March to Julj 

 1871, and figured, with description, as spermatozoa of these 

 sponges, in the following December (Schultze's Archiv fiir 

 Mikroscop. Anat. vol. viii. pt. 2, p. 281), I found in Microciona 

 atrosanguinea^ at Budleigh-Salterton, Devon, in July 1870, 

 and fully described them as such in the following October 

 (Annals, vol. vi. pp. 339,340) — conjecturally, it is true, because 

 I do not know tliat any one has yet seen them pass into the 

 ovum of the sponge, which is thus still wanting to confirm the 

 otherwise well-assumed fact. My description is unaccompanied 

 by illustrations ; but the figures in my journal, from which it 

 was taken, are identical with those of Eimer, and therefore the 

 description too. 



The " thread-cells " which Eimer figures from the Eenie- 

 ridae &c., at p. 283, ^*^., I have not yet seen. 



I could have wished that Eimer had alluded to my descrip- 

 tion of October 1870 instead of quoting Hackel's account of 

 mine and Prof. Huxley's figures respectively (published in 

 the ^Annals,' in 1854 and 1851) of spermatozoa in the 

 sponges, as explained by Lieberkiihn, whose identification 

 of the latter with a flagellated infusorium is now shown by 

 Elmer's figures to have been most unfortunate — and as regards 

 my own, doubtfully given from the first (in 1854, and contra- 

 dicted in 1858) as spermatozoa, equally unjust ; for although 

 probably not the spermatozoa of Spongilla, there can be no 

 doubt that they really belonged to it, and, by their habits, 

 could not have been the infusorium mentioned by Lieberkiihn. 

 In short, had Lieberkiihn read my description as well as seen 

 the figures, he would not have suggested this explanation. 



Eimer states, in his " Addendum," that Hackel has also 

 now seen spermatozoa in both the siliceous and calcareous 

 sponges (Jenaisch. Zeitschrift, vol. vi. pt. 2). 



Development of the Spicule. 



While the opportunity was afforded of tracing the develop- 

 ment of the ovule generally in the two Tethyce mentioned, 

 it will not seem unlikely that I should have endeavoured to 

 find out something more of the development of the spicule 

 than is stated in my " Ultimate Structure of Spongilla " 

 (Annals, 1857, vol. xx. p. 23) ; but I could not, so far as its 

 earliest and primary form is concerned (that is, the simple 

 acerate one), although I have been able to do so as regards its 

 arms or appendages. It should be understood, however, that 

 I am not going into the whole of the development of the spicule 



