ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
6l 
rods, which secrete by their distal extremity a refractive or crystalline 
body ; the anterior refractive portions of the rods form the vitreous 
body, the median pigmented parts the retina, and the thread-like ends 
put the rods into relation with the nerve-cells of the ganglionic layer. 
A similarly simple eye has been described by Fraisse in the molluscan 
Fissurella grseca . 
The cervical organ may be in the form of ciliated pits, ciliated fins, 
ciliated or non-ciliated epaulettes ; they always consist of much elongated 
epithelial cells encrusted at their base with direct prolongations of the 
brain or with large nerves which are given off from its hinder portion. 
A synonymical table is given of the very various names that have 
been applied to the different portions of the pharynx, which is in all 
cases lined by a thick layer of chi tin. The proventriculus is essentially 
formed of radial columns of muscular substance disposed around the axis 
of the organ ; each row is separated from the next by a transverse 
fibrillar diaphragm. Considerable 'differences are exhibited in the con- 
struction of these columns. 
The vascular system is very simple, and has no superficial ramifica- 
tions, though respiration is purely cutaneous, except when it is effected 
by the digestive tube. The nephridia do not play an important part in 
excretion, but at the period of reproduction they increase considerably 
in size, and serve as efferent ducts for the genital products. 
Reproduction is effected by schizogamy (misnamed alternation of 
generation) in which a sexual bud separates from a non-sexual stolon, 
and epigamy (so-called direct reproduction), in which the whole of 
the individual acquires secondary sexual characters at the time of ma- 
turity. The formation of stolons may be effected by gemmation or 
fission. Schizogamy and epigamy may exist independently of one 
another, but the distinction is not of generic value, while there are 
some forms in which both modes of reproduction are to be seen. 
The different modes of growth of the body are fundamentally forms 
of one phenomenon — the production of zoonites ; the tissues contained in 
a formative zoonite are not differentiated, but at the same time one may 
recognize in them the three primary layers. The differentiation of 
tissues may be followed in proceeding from behind forwards. At sexual 
maturity the reproductive elements lie freely in the general cavity and 
compress the intestine. 
The segmentation of the ovum is epibolic, and the larva is achaetous. 
The larva may have a musculo-glandular pharynx (“ larve monopharyn- 
gienne ”) which may be free, or it may also have a proventriculus (“ larve 
dipharyngienne ”) ; the latter type is peculiar to the Syllideae. The 
larvae leave the eggs at different times in different forms. 
With regard to the appendages of the cephalic segment and their 
homology with the appendages of other segments, the author gives the 
following table : — 
Anterior lateral antennas = Ventral rami. 
Median antennae = Dorsal cirri. 
Palpi = Ventral cirri. 
Posterior lateral antennae = Dorsal rami. J/ 
The author believes that the segments of the Annelid type are all 
morphologically similar, and that their constitution is determined by 
serial repetition and bilateral symmetry. 
