THEIR DEVELOPMENT. 41 



tions of these substances produce this effect only when they are so con- 

 centrated as to act chemically on the organic substance of the spermatic 

 filaments. 



Pure water at first accelerates the movements and then arrests them ; 

 at the same time causing the filaments to become twisted on themselves 

 so as to form loops. The latter effect is produced in the most remarkable 

 manner in the hair-shaped filaments of the invertebrata, and in less degree 

 in the pin- shaped filaments of reptiles and Mammalia.* 



5. Great additions have been made to our knowledge, of the process by 

 which the spermatic filaments are formed, and the theory of their develop- 

 ment has been much simplified. Kolliker, the most successful labourer in 

 this field, proposed in 1841,| the law "that the seminal filaments are 

 developed either within cells, or by the transformation of cells, which are 

 formed in the testes at the time of puberty or of heat ; the processes of 

 development being analogous to those by which other elementary parts of 

 animals are developed." And he referred the modifications of these modes 

 of development to the following types. 



Type I. Each spermatic filament is produced from a single cell by the 

 elongation of the cell itself. 



Type II. An entire fasciculus of filaments is produced from each 

 cell, by this first assuming the cylindrical form and then becoming resolved 

 into filaments. 



Type III. A fasciculus of many filaments is formed within the cavity 

 of a large cell. 



Type IV. Each filament is formed within a separate cell. 



Type V. The filaments are developed in fasciculi from finely granular 

 cells, by the component granules of the cells coalescing in linear series, so 

 as to form fibres, which then increase in length. 



Only the third and fourth of these types were observed by Kolli- 

 ker in the vertebrate classes of animals. The third type was, in fact, 

 the mode of development of sperm atozoid discovered by Wagner in 

 birds.J The fourth type was discovered by Kolliker in the guinea-pig 

 and mouse. The first stage in the process here observed by him, was the 

 existence of large cells varying from T g- to -L of a line in diameter. 

 The smaller of these cells contained one or two granulated cellules ; the 

 larger cells filled with similar cellules. These granular cellules measured 

 from ^j to giff of a line in diameter. They were set free by the solution 

 of the large parent cell, and then within each of them a spermatozoid 

 made its appearance, the granules previously contained in the cellule 

 disappearing at the same time. The body of the spermatozoid seemed to 

 be formed by the coalescence of a large number of the granules. The 



* Wagner's Physiologic. 



t Beitrage zur Kenntniss der Geschlechts-verhaltnisse und der Samenfliissigkeit wirbel-loser 

 Thiere. Berlin, 1841, p. 53. See pp. H75-6 of Muller's Physiology. 



