Nro. 2.] COMPARATIVE CVTOLOGICAL STUDIES . 
caused by (i) the direct action of the fluid of Flemming, or 
more probably (2) they might be post-mortem exudations of the 
nucleoli, which might well be produced before the slowly pene¬ 
trating fixative had reached to the cells in question. At any 
rate, they cannot be regarded as normal structures. Do they 
represent the “ Kernkorperchenkreis ” of Eimer ? 
The chromatin, as in Doto , occurs in the form of granules, 
which are connected by fine fibers. After fixation with Klein- 
enberg’s fluid a clear space encloses each nucleolus (Figs. 93 
and 94); but this space is not to be found after fixation in 
other fluids. 
As in Doto , the nuclei of the colossal ganglion cells contain 
a relatively greater amount of nucleolar substance than do those 
of the second and third types. But in the former genus there are 
in the colossal cells from about six to thirteen nucleoli, and these 
vary noticeably in size and structure, while in Montagna there 
are only from one to three, which are always homogeneous and 
usually quite equal in dimensions. Why should there be this 
marked difference in the form and number of the nucleoli ? 1 
14. Ganglion Cells of Piscico la rap ax (Verr.). 
(Plate 23, Figs. 134-136 ) 
In the ganglia of the brain occur cells of different dimen¬ 
sions. Each nucleus contains most usually a single small 
spherical nucleolus; seldom are there two present, and in these 
cases they are unequal in size. None of the nucleoli contain 
vacuoles. They are excentric in position, but are never in 
contact with the nuclear membrane. These nucleoli are small 
in proportion to the size of the nucleus. 
15. Muscle Cells of Linens gesserensis (O. F. M.). 
(Plate 21 , Figs. 51 - 56 .) 
(The nuclei of the circular muscular layer of the body wall 
were studied. Those of Cerebratulus lacteus Verr. are essen- 
1 For other observations on nucleoli in ganglion cells of molluscs, cf the 
reviews of the papers of Pfliicke (’95), Leydig (’83), and Rohde (96). 
