ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
21 
Amici differs from the sturgeon in the mode of its brain development, 
mainly in its tendency to differentiate the roof of the epencephalon 
and to reduce the calibre of the infundibulum. The transitions towards 
Teleostean conditions are noteworthy. In fact the brain of the bony 
fish is so closely Amioid that it may reasonably be looked upon as but 
a high degree of specialisation of this neo-ganoidean type. The ap- 
pearance of the hypophysis is late and inconspicuous. There appears 
to be no evidence that the auditory sac appears as in Serranus. The 
sucking discs are s|)ecialised pit-organs or sense-buds, precociously 
developed and enormously enlarged. Indeed precocious development is 
one of the most striking general features in the organogeny of Amia. 
The general systematic conclusion is that the development of Amia 
confirms the palaeontological evidence as to the derivation of Clupeoid 
Teleosts from Amioid Ganoids. 
Blastoderm Margin in Salmonidas.* — Herr Fr. Kopsch describes 
some experiments on trout embryos, which go to show that a concrescence 
in the manner formulated by His does not occur in Salmonidae. On the 
cellular ring or margin of the blastoderm an embryogenic region must 
be distinguished from a portion which is not directly formative. In the 
embryogenic portion, which lies in the position of the first invagination, 
the portion near the middle line, whose cells form the head, must be 
distinguished from the cell-groups on each side, which in the course of 
development meet in the middle line and form the kuob or Knopf. This 
represents a centre of growth from which trunk and tail are formed. In 
this formation, cells belonging to the non-formative portion do in the 
course of the growth round the yolk reach the Knopf and are there used 
in the formation of the embryo. 
Syncytium in Cleavage of Belone acus.t — Herr J. Sobotta describes 
an interesting stage in the development of this fish. When there are 
about eighty cells formed, the centre of the blastoderm develops quickly 
and becomes several layers thick, while the periphery remains a single 
layer. A few minutes later the peripheral cells become indistinct and 
form a syncytium. This happens repeatedly. The whole yoke syncytium 
in this case is observably due to a fusion of blastomeres. 
jS. Histology. 
Relation of Centrosomes to Cytoplasm.;]; — Herren K. Kostanecki 
and M. Siedlecki report at great length on the results of their study of 
Ascaris ova. 
The attraction spheres merely represent areas free from vitelline 
substance. It is important, however, to distinguish the c; microsphere, 1 ” 
a particular portion of the whole mitom or aster, representing a special 
differentiation of the rays in the centre of the radiation. A detailed 
discussion of the archoplasm results in the conclusion that this conception, 
in Boveri’s sense, cannot be sustained. 
Throughout the whole cell there is a fine framework of plasmic 
threads, ending peripherally in a distinct marginal zone. The plasmic 
* Verh. Anat. Ges. X. in Anat. Anzeig. Erg. Hft., xii. (189G) pp. 113-27 (10 figs.). 
•f Tom. cit., pp. 93-100 (5 figs.). 
% Arch. f. Mikr. Anat., xlviii. (1896) pp. 181-273 (2 pis.). ] 
