Prof. E. Claparéde on the Structure of the Annelida. 358 
' Reproductive Apparatus. 
The reproductive apparatus of the Annelida has hitherto been 
very imperfectly known. Numerous works have indeed thrown ° 
fresh light upon the educatory organs, known, since Dr. Williams 
wrote upon them, by the name of segmental organs. But as 
regards the sexual glands our knowledge has made but little 
progress for the last thirty or forty years. This memoir will, I 
hope, make known these organs in a satisfactory manner in a 
great number of species. M. Ehlers limits himself to saying 
that the sexual glands may be referred to a single fundamental 
type—namely, that of a coherent cellular mass, engendered on 
the inner surface of a part of the wall of the body, or on the 
dissepiments. This statement is true in many cases. M. Krohn 
saw the ovules make their appearance as a sort of epithelium on 
the surface of the dissepiments in Alciope; and I have myself 
made perfectly similar observations on Protula Dysteri. This 
rule cannot, however, be regarded as general. The sexual glands 
often present themselves under perfectly different conditions. 
The observations of M. de Quatrefages relate chiefly to the 
Nereida and Eunicea. He has seen the sexual elements make 
their appearance in these Annelida in a glandular organ extended 
beneath the abdominal nervous chain. This description is at 
any rate very inaccurate, as will be seen hereafter on reading 
the exposition of the singular construction of the sexual glands 
in various Lycoridea &e. 
The distribution and structure of the sexual glands in the 
' Annelida is subject to numerous variations, which will be illus- 
trated by a multitude of examples in the course of this memoir. 
Nevertheless the following form may be regarded as the most 
generally diffused among the Annelida :—The sexual glands form 
more or less complex racemes or networks of cords, the axes of 
which are occupied by sanguiferous branches, which are often 
contractile. The sexual elements in course of growth form ruffs 
all round the vascular axes, and become developed at the ex- 
pense of a layer of nuclei contiguous to the vessel. In the females 
the ovules are often in immediate contiguity to each other in the 
ovary ; but sometimes (in Owenia, Delle Chiaje, and some species 
of Polynoé) each of them is enclosed in a special ovisac. In all 
cases the ova, when arrived at maturity, detach themselves from 
the ovary, either immediately, or mediately by the rupture of the 
ovisac. For the most part the spermatozoids likewise detach them- 
selves from the testes to float freely in the perivisceral cavity. 
‘This fundamental form undoubtedly sometimes undergoes 
important modifications—for example, to produce the singular 
sexual tissue of the Nereidea or the floating testes of the Dasy- 
Ann. & Mag. N. Hist. Ser.3. Vol. xx. 24 
