298 M. Krohn on the Anatomy and 



aggregations that the spermatozoa are subsequently developed. 

 Their size varies in the different individuals, and they are more 

 numerous in proportion as they are younger. In the greater 

 number of individuals, below or little above the mean size, only 

 these aggregations of cells are met with; when the animals increase 

 in size their number visibly diminishes, by their transformation 

 into spermatozoa. Lastly, the seminal cells of the adult individuals 

 contain, shortly before fecundation, only spermatozoa. The cells 

 which compose the seminal globules are all of the same size, do 

 not adhere together by any apparent means of union, and contain 

 numerous small granules, rarely a voluminous nucleus, which is 

 immediately rendered perceptible by the addition of dilute acetic 

 acid ; by this means also the sides of the cells containing them 

 become visible. The spermatozoa, which, as I have already stated, 

 become more numerous in proportion as the animal is developed, 

 appear under a variety of forms. Sometimes they are bodies split 

 in their middle into two prolongations or tails, more or less long, 

 following the same direction, receding more and more, termina- 

 ting in a point and forming amongst themselves an angle more 

 or less open ; at other times these tails extend in a straight line ; 

 at others again a third tail is added, which is directed laterally, 

 starting from the middle part, &c. The result of an attentive 

 examination is, that these varied forms may be attributed to the 

 differences which each of the successive phases of development 

 presents : thus we see a great number of very small tails deve- 

 loped upon a seminal globule, which may be compared to spurs ; 

 these prolongations, the first rudiments of the spermatozoa, al- 

 ready exhibit, at their base, traces of organization at its com- 

 mencement, which extends more and more, becomes general, 

 and advances in the same proportion as the volume of the sper- 

 matozoon increases. During these metamorphoses, the primor- 

 dial cells are very considerably modified ; they become smaller, 

 lose their granular contents, and, at a certain period, appear only 

 as simple appendages,- — filaments : these are the spermatozoa in 

 the process of formation. The masses formed principally of sper- 

 matozoa in the mature state are easily distinguished by their in- 

 tensely white colour, whilst the masses of less-developed sperma- 

 tozoa may be recognised by their faint white aspect. Probably 

 the spermatozoa become disaggregated at the period of their ma- 

 turity ; then, being free, they pass into the excretory canals, and, 

 propelled by the currents produced by the movements of the 

 vibratory cilia, they finally reach the hollow prominences. 



I should here mention a very remarkable phsenomenon which 

 occurs in the interior of the seminal cells. This consists in 

 slow, very manifest movements of the seminal globules and masses 

 of spermatozoa, which take place in a greater or less extent, and 



