298 M. Krohn on the Anatomy and 
ageregations 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 merease 
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 containmg 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 pomt 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, &. The result of an attentive 
examination is, that these varicd 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 thei 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 phenomenon 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 
