ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
183 
May, but winter-spawning is also lmown. Two eggs are laid almost at 
the same time ; the blunter end emerges first ; the mother fish seems by 
her movements to secure the entangling of the tendrils of the egg-case. 
When the egg is laid the blastoderm is in a morula stage, and the dis- 
position of the blastoderm disc has no constant relation to the main axes 
of the egg. 
Between the temperatures 11° and 16° C. the stage reached is a 
function of time and temperature ; thus if a stage x be reached in six 
days at 10° C., the same will be reached in four days at 15° 0. 
Formative Forces.* — Prof. Fr. Merkel discusses the forces which 
give shape to the animal body. He distinguishes the vegetative forces 
which sustain metabolism and growth from the formative forces which 
regulate structure. He supposes that both are resident throughout the 
cell and in every minute part. He refuses to accept the famous “ Igno- 
rabimus ” of Hu Bois Keymond, believing that Biology is really making 
some progress towards an understanding of the mysteries of growth and 
development. 
b. Histology. 
Intercellular Bridges in Muscle.t — Herr E. Hoehl has followed 
some others in pointing out that the intimate association of connective 
tissue and muscular tissue may give rise to a false appearance of inter- 
cellular bridges. In smooth muscle this seems particularly clear, 
though the existence of bridges is not denied. He also contends that 
the connective tissue sheath in the striped muscular tissue of the ex- 
tremities and heart is in all probability identical with the sarcolemma. 
Cell-Membranes.* — M. Louis Querton has written an interesting paper 
on the mode of formation of cell-membranes. The most important part 
is that which deals with the formation of the chitinous cuticle in in- 
sects ( Tenebrio molitor ) and in Crustaceans ( Garcinus meenas). There is 
nothing to warrant the conclusion that a peripheral plasmic layer is 
directly transformed into chitin. Vacuoles appear in the hypodermic 
or epidermic cells ; these open on the surface, and disappear. There is 
evidently a process of cellular secretion. 
Minute Structure of the Liver-Cell.§ — Dr. G. Schlater finds that 
the liver-cell has an extremely complicated structure. The nucleus and 
the cell-substance form an inseparable unity, “ a true organism.” There 
are several different kinds of differentiated elements or cytoblasts which 
produce the intercytoblastic substance (the plasmic network -f- the linin- 
framework). The various cytoblasts, distinguishable by physico-chemical 
peculiarities, have a definite topographical distribution in the cell, like 
organs in fact, and even the intercytoblastic substance seems hetero- 
geneous. It is different in the nucleus and in the cytoplasm ; and the 
cytoblasts of the nucleus differ in nature and disposition from those 
outside. The real elemental parts of the cell are these said cytoblasts. 
* Nadir. Iv. Ges. Gottingen, 1897, pp. 84-97. 
t Anat. Anzeig., xiv. (1 898) pp. 253-6 (3 figs.). 
% Ann. Soc. Belg. Micr., xxii. (1897) pp. 61-74. 
§ Anat. Anzeig., xiv. (1897) pp. 209-23 (11 figs.) : 
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