17-1. [April, 



the ring; formed of the mentioned cells appears more distinctly, and by crushins^ 

 the animal with some care the cells may be isolated, ami they will be seen to be 

 entirely identical with the animals described by Volkmann under the name of 

 Cosmella hydrachnoides. They are round cells with one or two nuclei, having 

 always four very long cilia, which are united in pairs and then fuse together in 

 the cell wall. The motion is a slow rythmical jumping, produced by alternating 

 contraction and expansion of the cell by which the cilia, if not called otherwise for 

 distinction, are made to act like the motion of a whip. But this power of the cells 

 producing the movement, must cause the latter to be considered as something 

 entirely different from ciliary motion, and, in fact, it appears as if a great many 

 different motions were understood under this term, the real nature of which have 

 not yet been studied. 



If we are led sometimes by first observations to the theory of generatio 

 ffiquivoca, as the facts here presented have done, repeated and more close obser- 

 vation brings us from this extraordinary theory always back to the old laws 

 Omne vivum ex ovo. The supporters of the generatio a-quivoca have certainly 

 lost in the separation of these cells from tlie number of animals, as much as by the 

 discovery that the so-called spermatozoa are but the changed nuclei of cells, 

 formed in the male genital organs of animals. 



As regards the particular movements in organic formations independent of the 

 nervous system, and even for a certain time independent of the mother animal to 

 which they belong originally, we have, at the present time, not less than four. 



1. The motion of corpuscles of sperm. Transformed nuclei of cells. 



2. Ciliary motion, roundish or cylindrical, perfect cells of epithelium on 

 free surfaces, with a number of cilia, which are in constant motion independent 

 of the cell. 



3. The Chromatophores of the Sepia. They cover the animal and produce by 

 their constant contraction and expansion, the beautiful colours which it presents. 

 For which reason, Rudolph Wagner, who first observed this interesting phenome- 

 non, called them Chromatophores? 



4. The fourth is a simple cell with four long hair-like appendages, as I have 

 described them. Here the cells contract and the appendages are by this property 

 set in motion. This form has only been observed till now in embryos, whilst 

 the first one belongs only to full grown animals, the ciliary motion is to be found 

 at any age, and the chromatophores only after the animal, which is provided with 

 them, has come to its last type. 



The Committee on Prof. Meigs' Memoir, entitled " Observations on 

 the reproductive organs, and on the fetus of theDelphinus Nesarnak," 

 reported in favour of publication in the Journal of the Academy. 



The Monthly Keport oi' the Corresponding Secretary was read and 

 adopted. 



Dr. Lcidy having stated that Prof. Agassiz was very desirous of 

 havinfT a drawing and engraving made in Boston of the skull of a 

 Manatus, in the cabinet of the Academy, on motion of Dr. Ehvyn, 

 Art. 1, Chap. viii. of the B3'-Laws was suspended for one month, 

 in order to comply with the request of Professor Agassiz. 



ELECTION. 



Thomas Pennant Barton, Esq., of Philadelphia, was elected a 

 ^Member of the Academy. 



