4 iS 
MONTGOMERY. 
[Vol. XV. 
present in none of the ova, though here the same stages of 
the ova were present as in the first individual. When they 
occur it is only in the larger germinal vesicles. They are 
apparently structures sui generis y and I have only the sugges¬ 
tion to offer, that they might be characteristic of a particular 
generation of egg cells, as their absence in the ova of some of 
the individuals of the mollusc would render probable (compare 
the observations of Hacker, ’ 93 a, where nucleolar differences 
were found in the ova of primiparous and multiparous individ¬ 
uals of Cyclops strenuus ). 
In Fig. 70 is a remarkable case depicted, namely, two small 
nuclei lying within a larger germinal vesicle, the former having 
apparently been assimilated by the latter. 
2 . Do to. 
(Plate 22 , Figs. 64 , 68 , 69 .) 
The nucleolar differentiation of these ova is essentially as in 
Montagna , so that no detailed description of the process need 
be given here. But in the five individuals of Doto which were 
sectioned, no traces of pseudonucleoli were seen, and the nutri¬ 
tive globules within the nuclear sap are usually smaller and 
much more numerous than in Montagna. The yolk globules 
also have different shapes in these two genera. 1 
3 . Amphiporus glutinosus (Verr.) 
(Plate 24, Figs. 140-158.) 
(For descriptions of the connective-tissue elements of the 
nemerteans, from which the genital products are derived, cf. 
my previous paper ’96.) 
In the nuclei of the connective elements, by a differentia¬ 
tion of which the ova are produced (without any intervening 
1 For the observations of other authors on molluscan germinal vesicles, cf. the 
reviews of the papers of Wagner (’35, ’39), Flemming (’74), O. Hertwig (’78b), 
Lonnberg (’92), Balbiani (’65b), Platner (’ 86 ), Leydig (’55a, ’50), Stauffacher 
(’93, ’97), Stepanoff (’65), Loven (’49), Mark (’81), List (’96), Blochmann (’82), 
Trinchese (’80), Heuscher (’93), Hubrecht (’81), Carnoy (’84, ’85), Wiren (’92), 
Fol (’89), Lacaze-Duthiers (’57), Quatrefages (’49). 
