1849.] 



173 



April 2ith, 1849. 

 Mr. Phillips in the Chair. 



The Committee to whom was referred the following communication 

 from Dr. Keller, reported in flxvour of publication in the Proceedings. 



On Ciliary cells in some maritie nahed Molhtsca, in embryo. 



By WiLHF.Lii Keller, M. D. 



In following the development of the ova of different species of EoHs, of the 

 Acteon viridis, and of a little mollusk lately found and described by Mr. Agassiz 

 under the name of Cantops Harvardianus, I often noticed in the surrounding 

 transparent zona, which is falsely considered by authors generally as the white 

 of the egg, one or two, seldom more, small moving bodies, which were first ob- 

 served by Professor Volkmann,* who considered and described them as animals. 

 The circumstance that the motion is more a rythmic jumping, not very un- 

 like to that of the moving corpuscles of the sperm, and the observation that 

 it always occurs in the same degree of perfection, and only in those eggs in 

 which the cilia at the cephalic end of the embryo have attained their highest 

 development, caused me to think that those moving bodies might be nothing more 

 than detached ciliary cells of the embryo itself, an opinion which I afterwards 

 found advanced in a note by Professor Charles Vogt,t in his treatise on the devel- 

 opment of the Acteon viridis. To solve this question seemed to me important 

 enough to try the experiment of isolating some of the cells from the animal. 



Before I describe the cell itself I will mention its development, and connection 

 with the animal. So soon as the eggs of the above named animals are laid, they 

 begin immediately the process of division, and when. this process has so far ad- 

 vanced that the yolk globules are so small that they seem to have disappeared, 

 ciliary motion appears at the edges of the yolk. The embryo, so soon as the 

 cilia are formed, rotates sometimes to the right side, sometimes to the left, and 

 changes the direction so soon as there is the least impediment opposed to it. The 

 rapidity of the motion varies; I counted seventy rotations in a minute. The next 

 change in the embryo is real cell formation. There appear cells towards the in- 

 ferior end, which I consider as liver cells ; and which are mother cells, contrary 

 to Professor Vogt's opinion; two cells in the head, the ear cells containing three 

 cells, and a ring of cells provided with long cilia around the head. In the mean 

 time the other cilia are disappearing. The embryo is now no more unconsciously 

 rotating, but the whole body is stretched out, and the only motion observed in it 

 is performed by the long cilia, which are seen folded together like a fan, or 

 playing like the wheel of rotiferous animals. This motion changes very often 

 and seems to be entirely under the control of the animal itself, notwithstanding 

 the animal does not show any formation of nerves, as it only consists of cells at this 

 period, and there is no fibrous structure to be perceived, so that the embryo 

 of these higher animals shows, at least apparently, voluntary motion without a 

 nervous system like the lowest orders of the animal kingdom. By some pressure 



• Versuch einer Monographie des Tergipes Edwardsii," read before the Acad- 

 emy of St. Petersburg, Feb. 9th, 1844. The author calls these cells Cosmella 

 hydrachnoides, and considers them as an instance of spontaneous generation. 



fRecherches sur I'Embryogenie des Mollusques Gasteropodes par M. C. Vogt, 

 prssenteea a I'Academie des Sciences le 2 Mar. 1846. 



