ANN U LATA. 



257 



Sperm-cells and spermatozoa, Lumbn'cus. 



Exogone or Cystonereis. In the females the middle segments exhibit 

 pyiiform sacs, attaclied to tlieir ventral surface, which receive tlic 

 ova alter they are iinpi'egnated ; the male is without these and is 

 smaller. Tlie genus Eunice is viviparous, and the young escape from 

 the ruptured skin of the hinder segments. 



Finally there remains to be considei'ed the development of the ge- 

 nerative products. As to 

 the spermatozoa, these are 

 formed in a number of cells 

 connected together by a 

 spherical mass, and stud- 

 ding its surface. {Fig. WO, 

 A.) Each cell is the seat 

 of development of a sepa- 

 rate spermatozoon, and this 

 in its growth pushes the 

 cell-wall outward : the fila- 

 mentary extremities di- 

 verse from the common 

 basis of the sperm-cells 

 (c) ; then, by mutual attraction, they become amassed together (d) ; 

 and the bundle is finally resolved into the individual spermatozoa (li). 

 Dr. A, Farre has communicated to me the following phenomena 

 which he witnessed during microscopical observations of the sperma- 

 tozoa of the earthworm. He placed the contents of the testis between 

 two slips of glass. " In about ten minutes the whole mass is seen to 

 heave and writhe with astonishing energy, the form of the movement 

 being that of the peristaltic action of the intestines. Everything in 

 contact with the spermatozoa becomes ciliated by them, one end of the 

 filaments fixing itself whilst the other vibrates free. The result is, 

 that if the body to which the spermatozoa attach themselves is fixed, 

 such as the glass, on the margin of a mass of granules, a line of cilia 

 is formed, whose action creates a strong current, and everything 

 moveable is drawn into the vortex, and is seen drifting rapidly along. 

 But if the body to which they attach themselves is moveable, such as 

 the globular bodies found in the testis itself, or those which occur in 

 every part of the ovary, and which, being extracted from the latter, 

 are placed, for the sake of experiment, amongst the spermatozoa from 

 the testis, then the globular bodies soon become clothed with sperma- 

 tozoa, whose free ends, moving rapidly, cause the whole body to rotate. 

 A most remarkable object is thus formed, which continues for a con- 

 siderable time in motion, clearing for itself a free area, and in this it 

 revolves, whilst its revolutions are apparently assisted by the action 



s 



