482 



SEMEN. 



tened. The posterior end is continued into the 

 tail, which latter is tolerably thick, and almost 

 straight at its commencement. It gradually, 

 however, assumes a very thin appearance, 

 becoming a very attenuated hair-like ap- 

 pendix, which exhibits the same spiral wind- 

 ings that occur among the Salamanders. The 

 length of the spermatozoa, as far down as 

 where the tail bends itself, amounts to ^V" 



-A."'. 



Another very singular form of spermatozoa 

 is met with in Pelobates fuscus. The sperma- 

 tozoa measure J/"- There is no boundary 

 perceptible between the body and tail part, 

 but one half of the spermatozoon distinguishes 

 itself from the other by a considerable thick- 

 ness. Both, however, gradually pass into one 

 another. The thicker part exhibits from its 

 commencement a number (generally eight) of 

 spiral windings, which increase in size towards 

 the anterior free end (/g.342.). The anterior 



Fig. 342. 



the cell of developement continue for a long 

 time adhering to the body of the spermatozoa, 

 generally in the centre, exhibiting the appear- 

 ance of a comb-like appendix of a variable 

 shape and size. 



The formation of the spermatozoa in the 

 interior of independent cells of developement 

 likewise takes place in a similar manner in 

 the Lacerta crocea. We have but rarely seen 

 that the same cells are enveloped by larger 

 cysts at the period of the production of the 

 spermatozoa, which is commonly the case in 

 former stages of the developement. The num- 

 ber of cells contained in one common cyst is 

 generally only very small, seldom exceeding 

 eight. The same is found, according to the 



Fig. 343. 



Spermatozoa of Pelobates fuscus. 



end itself does not however participate in this 

 formation. It is of a more delicate quality, 

 paler, and has a constant vibrating motion, 

 which gives to it a varying form. It generally 

 appears to be wound in an undulating manner. 

 A fascicular group of the spermatozoa 

 is only found among the Rcptilia in Batra- 

 chians ; Bombinator, however, forming an ex- 

 ception. In the latter, as well as in the scaly 

 Reptilia, the spermatozoa lie confusedly toge- 

 ther. In the latter instances we can readily 

 trace thtir production in the interior of se- 

 parate solitary cells of developement ; as, for 

 instance, in Anguis fragilis, or Bombinator 

 isrneus. The culls of developement of the 

 latter animal (which to the number of two or 

 four are enclosed by a mother cell, when 

 in the earlier stages of developement) mea- 

 sure in a developed state about T -;/". At 

 first, when the spermatozoon forms itself in 

 the interior of these cells, it lies curled up close 

 to the wall. Subsequently the fibre stretches 

 itself, and changes the cell into an obtuse 

 cylindrical enclosure, which finally bursts in 

 the anterior and posterior part, to enable the 

 tpermatozoon to make its exit. The remains of 



Cells of developement of Testudo graca with Sperma- 

 tozoa and external cysts. {After Kolliker.) 



observations of Kolliker, in Testudo graeca ; 

 but the external cyst in this instance is said 

 generally to persist for a longer period. The 

 persistency of this enclosure is very general 

 among the Batrachians, which distinguish 

 themselves by the spermatozoa being asso- 

 ciated in fasciculate groups. The number of 

 the enclosed cells of developement here is 

 generally a larger one (from ten to twenty). 

 The developement of the spermatozoa in 

 other respects does not, however, exhibit 

 anything peculiar. They are formed as 

 usual, separately in the enclosed cells of de- 

 velopement (Jig. 344.). It is only afterwards, 



Fig. 344. 



Developing cell of the Frog, with a Spermatozoon in 

 its interior. {After Kolliker.) 



when these cells have been dissolved, that 

 the spermatozoa get into the interior of the 

 mother cyst, in which they congregate in 

 fasciculate groups. By their so doing the 

 cyst loses its original round shape, and as- 

 sumes the form of a pear, until it bursts at 

 the pointed extremity, and the tail-ends of the 

 spermatozoa immediately project. The re- 

 mains of the cyst continue recognisable for 

 some time at the anterior end of each bundle. 

 This is the case in the frog at any rate. In 

 Pelobates, on the other hand, the filiform 

 tails of the spermatozoa do not project from 

 that part of the cylindrical enclosure which 

 is burst, but the anterior vibrating body docs 

 so (fig. 345.). 



The external cyst of the bundles of sperma- 

 tozoa of the Salamander constantly retain 

 its original globular shape, as the sperma- 



