SPERMATIC PARTICLES. 46 



molecular, and are indicative of the higher vitality of these molecules. We have yet 

 to learu every thing about any animal motion, and my own impression is, that all 

 (muscular, &c.) will be found to be essentially molecular, or belonging to molecules, 

 which are the first expressions of vitality, and serve as the basis of all organized 

 tissues whatsoever. During my investigations, I have tried the influence of various 

 agents. Electricity had no well-marked effect. But all those chemical agents that in- 

 fringed affinitively upon the material structure, thereby impairing their integrity and 

 vitality, put a stop to the motion. All my own experiments went to show that all 

 these movements were identical in character with those of the cilia of epithelial cells, 

 a matter that I have fully discussed in another place.* 



Signification of Vitelline Segmentation. 



Before closing this interesting subject, I have thought it essential to a clear un- 

 derstanding of the whole ground of analogy existing between the sperm-cell and the 

 true ovum, that a survey should be taken of the process of segmentation and its 

 meaning, since it forms the basis of the analogy. We will take it up as studied 

 with the ovum. 



The earliest phases of change the observer is able to perceive with the fecun- 

 dated ovum is the fissuration of the vitellus. Upon a single surface of the vitellus, 

 a kind of retreat of substance from a given point occurs ; this produces a slight sulcus, 

 which, deepening, divides the vitellus into two spheres. Upon each of these spheres 

 the same process is repeated, and this goes on increasing in a geometrical proportion, 

 until the whole is a granular mass. Succeeding this subdivision is the immediate 

 process of the embryo's formation. 



The true signification of the segmentation of the vitellus has not, I am convinced, 

 been fully understood. Noticed first by Prevost and Dumas f in the frog, it has since 

 been more carefully watched by Rusconi, f Baer,^ Bergman, || Ruchert, H Vogt,** 

 Agassizjft and others of a later day. It has, until quite recently, been considered 



* American Journal of Medical Science, July, 1849. 

 t Annal. des Sci. Nat., Tom. II. p. 129. 

 J Developpement de la Grenouille commune. Milan, 1826. 

 § Mailer's ArcJiiv, 1834, p. 481. 

 II Miiller's Archiv, 1841, p. 89. 

 ^ Muller's ArcJiiv, 1841, p. 523. 



•* Untersuchung Uber die Entwickelungsgeschichte von Alyles obslelricans, 1842, p. 3. 

 ft Lectures on Embryology. 1848. 

 VOL, V, NEW SERIES. 7 



