382 K. MASUL: 
animals two generations of spermatogonia can be distinguished, a penultimate 
and an ultimate. But as several generations of spermatogonia are found in 
one and the same testis this distinction is not quite positive. It is, however, 
convenient to distinguish two generations and to use MONTGOoMERY’S terms 
“ penultimate” and “ultimate” instead of “ primary ” and “ secondary,” used 
by various authors. Monrcomery’s (ll) view in using these terms in his 
study in Euschistus is as follows: “In the testes of adult individuals are 
found two generations of spermatogonia which it will be convenient to call the 
‘ penulimate,’ and ‘ultimate,’ these terms being preferable to ‘ primary’ and 
‘secondary’ of most writers, for the reason that primary and secondary 
employed in the striet sense should refer to the first two generations of the 
germinal cycle. Whether there are three generations of them in adults was 
not positively ascertained.” 
The resting nucleus of both spermatogonial generations usually contains 
one large nucleolus and|many small chromatin masses (Figs. 31, 32, 40). The 
nucleolus of the penultimate spermatogonia is more or less larger than that 
of the spermatogonia in the earliest generation (Figs. 4, 6, 31). It gives an 
appearance of granular construction composed of aggregated chromatin granules. 
These chromatin granules as well as those in the linin later begin to arrange 
themselves along fine threads (Figs. 33, 34). At the commencement of the 
prophase the nucleolus gradually disappears, leaving a plastin remnant behind 
(Figs. 33, 34). A similar condition has been fonnd by Jorpan (11) in opossum, 
where the function of the nucleolus is stated to favour the proposition that 
it plays “a part as a store-house of chromatin, which contributes at mitosis 
to the formation of chromosomes.” 
In the resting period of all the spermatogonial cells (in both adult 
and young animals) (Figs. 2, 31, 32), beside the large nucleolus, one 
rod shaped chromatin mass usually appears. It is difficult to determine 
whether this mass represents the future accessory chromosome or not, as it 
later disappears, and it is impossible to trace this chromatin mass during the 
metakinesis. In the resting period of the spermatogonia the chromatin 
nucleoli were found by WODSEDALER (13) in pig, and by BACHHUBER (16) 
in rabbit, both authors holding the view that the nucleoli and the accessory 
chromosomes are one and the same structure. In the prophase and the 
