124 
Society during the previous session, and contained the following 
additional notices : — 
Sertularia polyzonias , Linn. 
The gonophore of Sertularia polyzonias consists of an oval cap- 
sule slightly corrugated transversely, with a short tubular, obscurely 
4-toothed aperture, and having its axis occupied by a blastostyle, 
bearing in all the specimens examined a single sporosac. 
The sporosac is produced at first as a lateral bud from the blasto- 
style, but soon acquires an apparently terminal position, being borne 
on the summit of an axile peduncle formed by the portion of the 
blastostyle which intervenes between it and the base of the gono- 
phore, while the distal portion of the blastostyle seems to become 
more or less atrophied. The sporosac is furnished with a large 
simple manubrium, between whose ectoderm and endoderm the ova or 
spermatozoa are developed, the ectoderm retreating from the endo- 
derm more and more as the intervening generative elements increase 
in volume, while the endodermal portion of the manubrium, with its 
cavity, continues to occupy the axis of the sporosac, extending into 
the middle of the mass of ova or spermatozoa. For this endoder- 
^ mal portion of the manubrium, round which the generative elements 
are developed in the sporosacs of the hydroid polypes, I have 
already proposed the term spadix ;* while to the ectodermal layer, 
which now constitutes a sac immediately confining these elements, 
we may give the term endotheque , as distinguishing it from the 
ectotheque, or external investment of the sporosac. 
The ova and spermatozoa are of the usual form, and in the male 
sporosac the spermatogenous tissue may be observed in various 
stages of development. Towards the centre of the sporosac, where 
this tissue immediately surrounds the spadix, we find it in the con- 
dition of a thick mass of mother-cells filled with “ vesicles of evolu- 
tion but as we recede from the centre towards the walls of the 
sporosac, the spermatogenous tissue may be seen to have advanced in 
maturity, the mother-cells having burst and liberated their contents, 
while in immediate contact with the endotheque is a zone of active 
spermatozoa, which, when liberated, are seen to be of the usual form 
of minute caudate corpuscles. 
The generative elements are not absolutely confined to the spo- 
* British Association Reports for 1858. 
