ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
609 
the ovipositor tube. The latter is really a modification of the skin, 
which is retracted by a muscle and stretched by the entrance of an ovum 
and associated mucus. On the mature male there are well-known warts, 
which the author regards as integumentary modifications of the nature 
of tubular glands. The bitterness of the fish is due to the bile which is 
always abundant in the very large gall-bladder. 
Elimination of Nuclear Elements in Ovarian Ova of Scorpaena 
scrofa.* — Prof. Ch. Van Beneden has observed this in ovarian ova of 
the second phase — the phase of growth. The elimination affects the 
chromosomes only, the nucleoli take no part. After giving an account 
of analogous eliminations observed by other investigators, the author 
discusses possible interpretations. He does not think that there is any 
essential difference between the eliminating process and nuclear gemma- 
tion ; he is sure that the process is not artificial nor pathological ; it 
is a reduction of chromosomes. The eliminated elements are usually 
disposed in the vitellus at an equal distance from the germinal vesicle 
and from the periphery, but their fate is unknown. 
Experimental Embryology. — Prof. 0. Hertwig f has made a number 
of experiments with the developing ova of the frog, modifying their 
segmentation by gentle compression between two slides or by confining 
them within glass tubes. The deviations corroborate a conclusion which 
Hertwig stated, in 1884, that the two poles of the nuclear spindle, by 
which the direction of the segmentation-plane is defined, come to lie in 
the direction of the largest protoplasmic masses. Thus, in ova forced 
to assume a barrel-like form within a glass tube, the poles of the first 
segmentation always lie in the longitudinal axis of the tube. According 
to Hertwig, the results of his experiments, of which we have given only 
a general indication, go to show that it is not the segmentation which 
separates the ovum into qualitatively diverse parts such that each part 
has but limited developmental possibilities ; the predisposition is already 
in the unfertilized ovum. 
Herr D. Barfurth J criticizes recent work in regard to the terato- 
logical development of Ascidians. He opposes the conclusion of Chabry 
that the embryo obtained after the destruction of one of the two first 
blastomeres was a complete embryo of half size, and supports Roux in 
maintaining that a typical half-morula, half-gastrula, and a right or 
left half-larva is produced. He points out that Chabry describes the 
normal Ascidian larva as asymmetrical, the left eye and left otolith 
being undeveloped. In describing his teratological larvae, however, he 
describes them as complete, except that organs of “ slight importance,” 
such as the otolith or a fixing papilla, are wanting. By a detailed con- 
sideration of the larvae described by Chabry, Herr Barfurth endeavours 
to prove that these are in reality half-larvae, the complete appearance 
being produced by the fundamental want of symmetry or by the post- 
generation of Roux. By this means the divergent results of the two 
investigators are harmonized. 
Herr Barfurth also notes that in an investigation of his own as to 
* Bull. Acad. Belg., xxv. (1893) pp. 323-64 (2 pis.' 
t SB. K. Preuss. Akad. Berlin, 1893, pp. 385-92. 
i Anat. Anzeig., viii. (1893) pp. 493-7. 
