288 C. Mereschkowsky on Waguerella borealis. 
ternal conditions (aptera-terminalis), whilst at other times 
there are striking differences (renwm-crustalis). 
Whilst admitting that the two generations may have been 
originally identical, one is led to ask, which of the two now 
existing corresponds to the original form, or at least re- 
sembles it most. M. Adler believes that it is the agamic 
generation that represents this original form; if it is not 
identical with it, it should at least be very near. This con- 
clusion is deduced from the following facts :— 
First, the parthenogenetic form exists alone in certain 
species. 
Secondly, among the Cynipide there is no case known of 
a sexual form existing alone; all the sexual species are only . 
known to us as a link in a cycle containing an agamic 
generation. 
Without being absolutely convincing, the arguments of M. 
Adler have a certain value. To this we might add that, con- 
trary to what we see in other Articulata in which partheno- 
genesis exists, the sexual generations are the summer broods, 
and the parthenogenetic generations producing females 
are those which hibernate. Now the analogies with other 
insects would lead us to suppose that the hibernating genera- 
tion is the original, and that the summer generation is 
secondary*. 
These provisional hypotheses will probably have to be much 
modified by later discoveries ; but the researches of M. Adler 
will always be conspicuous as being a great advance in our 
knowledge of parthenogenesis, and be reckoned among the 
mostpatient and fruitful researches which have been undertaken 
on insects. A. H. 
“ XXVIII.—WNote on Wagnerella borealis, a Protozoan. 
By C. MrREScHKOWSKY. 
WHEN I described in this Journal} the interesting organism 
that I discovered in the White Sea, and named Wagnerella 
borealis, in honour of my master Prof. Nicolas Wagner, | 
had before me only a few specimens ; and these were preserved 
* See A. Weismann’s ‘Studien zur Descendenz-Theorie: [. Ueber den 
Saison-Dimorphismus der Schmetterlinge,’ Leipzig, 1875. 
+ C. Mereschkowsky, “On Wagnerella boreats, «1 new Genus of 
Sponge nearly allied to the Physemariez,” Ann. & Mag. Nat. Hist. 1878, 
ser. 5, vol. i. ; and “ Etudes sur les Eponges dela Mer Blanche,” in Mém. 
de l’Acad, de St. Pétersb. vol. xxvi. no. 7. 
