82 QUARTERLY CHRONICLE OF MICROSCOPICAL SCIENCE. 
white yelk in the case of the Batrachians. ‘The female sexual 
epithelium, which persists at the surface of the ovary of 
mammals, at the expense of which the ovarian tubes are 
formed, the vesicles of Von Graaf and the canals of Muller, 
are derived then in ultimate analysis from the endoderm. 
The testicle is formed at the expense of the Wolffian canals, 
according to the observations of Waldeyer and several other 
embryologists. Now, His, Hensen, and Waldeyer derive the 
Wolffian duct from the outer layer (ectoderm) by the inter- 
mediation of the axial cord. Accordingly, the testicle would 
also be derived in the Vertebrata from the ectodermic layer. 
My conclusions are thus confirmed, even at the present 
moment, as far as concerns the group of the Vertebrata.” 
Nemertine Worms.—The very handsome work of Dr. 
McIntosh published by the Ray Society has arrived at a 
second part, in which histological details and some embryo- 
logical facts are given with that excellence of illustration 
which renders the work so conspicuous among English con- 
tributions to modern zoology. 
Dr. A. A. W. Hubrecht, at present assistant to Professor 
Selenka, of Erlangen, prosecuted some interesting researches 
upon Nemertines at the Zoological Station, at Naples, 
during the spring of 1874. These furnish the subject for a 
Graduation thesis just published in Dutch, at Utrecht. New 
species and genera of considerable interest are described, as 
also the minute structure of the nerve-ganglia. Haemoglobin 
was detected by means of the spectroscope in the nerve tissue 
of two species of Meckelia, and in true red blood-corpuscles 
in Drepanophorus. An important developmental fact is estab- 
lished by Hubrecht’s observation (and figure) of the formation 
of an invaginate Gastrula (precisely similar to that of many 
Molluses), in the early stages of Borlasia olivacea. 
Nematoid Worms.—In Lacaze Duthier’s ‘ Archives,’ Ist and 
2nd parts for 1874, is a monograph, by M. Villot, on the 
‘Dragonneaux,’ or genus Gordius. The development of 
Gordius aquaticus within the egg and in subsequent phases 
of encystment is illustrated in the plates. This monograph 
will serve as a valuable guide to those who wish to pursue 
further the structure and development of these remarkable 
worms, since M. Villot has made a very careful study of their 
habits and migrations, as well as of their specific characters. 
M. Villot finds that the young Gordius aquaticus first makes 
its way into insect larvee (such as Chironomus), and becomes 
encysted, after which it finds its way with its host into the 
alimentary canal of fishes, where it is again encysted. It 
escapes from this position per anum in the spring. M. Vil- 
