86 



means of a small thermometer attached to the magnet, the stem of 

 which is parallel to the axis of the bar. In this thermometer, the 

 size of the bulb, its distance from the freezing- point and length of 

 the scale, may be so proportioned to each other, that the second as 

 well as the first term of the temperature coefficient will be repre- 

 sented in the correction. 



8. " On the Reproduction of the Ascaris Mystax." By Henry 

 Nelson, M.D. Communicated by Alien Thomson, M,D., F.R.S. 



Received May 22, 1851. 



The author commences with a brief anatomical description of the 

 Ascaris IWystax, found in the intestinal canal of the Domestic Cat ; 

 with more especial reference to the organs of generation in the two 

 sexes. Fie traces the gradual formation of the semen ; originally 

 thrown off as seminal particles by the caecal extremity of the tubular 

 testicle, the exterior of each solid particle enlarges to constitute a 

 cell, while the interior retains its consistency and forms a nucleus. 

 The cell then acquires a granular protecting envelope, and in this 

 state is introduced into the female. The solution of the protective 

 envelope and the great enlargement of the seminal cell follow, and 

 its nucleus is now seen to present a granular structure. The exter- 

 nal granules of the nucleus coalesce to form a membrane, at first 

 exactly resembling a watch-glass in shape, but by the contraction of 

 its margin ultimately forming a curved caical tube. This is the 

 true spermatic particle or spermatozoon, and is set free by the 

 rupture of the seminal cell. 



The generative apparatus of the female, commencing also in ca^cal 

 extremities, is next treated of, and the author draws particular atten- 

 tion to a transparent, narrow contractile portion, the oviduct, inter- 

 vening between the ovary and uterus, as the part in which the ovule 

 encounters the spermatic particles, and is by tliem fecundated. 

 The C88cal end of the ovary likewise throws oft' a solid particle, 

 which enlarging forms a germinal vesicle and spot. As the ger- 

 minal vesicle travels slowly down the tubular ovary, it acquires a 

 thick granular investment or yolk, secreted by the ovarian walls. 

 The ovules nov/ present a flattened triangular shape, are placed side 

 by side, and form one solid mass. At the commencement of the 

 oviduct however they become detached, separated from each other, 

 and propelled singly along its interior. Here the gelatinous ovule 

 meets the tubular spermatic particles, and is surrounded on all sides 

 by them. They are at first seen to be merely applied against the 

 ovule, but by degrees the margin of the latter presents a rupture, 

 some of the vitelline granules are displaced, and the spermatic par- 

 ticles become imbedded in the substance of the yolk itself. 



While the penetration of the spermatic particles is going on, a 

 chorion, secreted by the oviduct, surrounds the ovule, forming a 

 spherical envelope, within which the germinal vesicle, the granular 

 yolk, and the imbedded spermatozoa, are enclosed. The spermatic 

 particles after penetration are seen to swell, become transparent, and 

 ultimately to dissolve. The vitelline granules likewise either disap- 



