Encystment of Aiolosoma. 17 
knowledge of the cocoons of the Oligochata he observes with 
regard to Kolosoma, “ Auf die Schilderung der vermeint- 
lichen Cocons von -4olosoma wie sie seinerzeit Maggi 
gegeben hat, verzichte ich einzugehen, da es hier durchaus 
unklar bleibt, ob er thats&chlich Cocons, oder encystirte 
Wiirmer gesehen hat.” I am not certain whether Prof. 
Vejdovsky is speaking here of his own knowledge or is 
merely arguing from Maggi’s figures ; be that as it may, | 
believe that Vejdovsky’s suggestion of encystment is the 
right one, and I had come to that conclusion before making 
myself acquainted with the paragraph quoted above, while 
getting together the literature of the subject. All the facts 
that I have been able to bring forward in this paper tend, as 
it appears to me, to show that we have here a unique case 
among the Oligocheta of encystment. I believe [ am right 
in saying that no freshwater Annelid has hitherto been dis- 
covered to possess this power of temporary encystment. I 
shall now endeavour to show that Molosoma does encyst 
itself, 
On the hypothesis that the cysts in question are cocoons 
we have to dispose ef a good many preliminary difficulties. 
In the first place their form—absolutely spherical and without 
processes at either end—is unique among the Oligocheta ; 
Aivlosoma of course may be an exception, “but there is not, I 
think, evidence at present that it is. Secondly, there is the 
difference of size; no doubt there are infinite variations in the 
size of the cocoons of various species of Oligocheta, but I 
have not found such a great difference as I have recorded here 
among the cysts of @olusuma. 'Thisvery fact seems toindicate 
that Maggi’s figures, to which I have already referred, repre- 
sent cysts (of various sizes) and not developing ova; the 
figures of the contained embryos which he gives are not sufti- 
ciently detailed to enable one to be absolutely certain that 
they are not disintegrating worms rather than developing 
embryos. ‘The difference in shape between the structures 
figured by Maggi and those which I have observed may be 
possibly put down to specific differences. Thirdly, all the 
cysts which I examined — amounting to forty or fifty — 
contained fully grown worms, immature certainly (as regards 
absence of sexual organs), but quite as large as those 
swimming about in the same water. ‘This may be merely a 
coincidence, but in that case it will be a very remarkable one ; 
all that we know of the development of the Oligocheta shows 
that the time varies somewhat in individuals, one growing 
faster than another. Besides this we have further to assume 
Ann. d&: Mag. N. Hist. Ser. 6. Vol. ix. 2 
