ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 175' 
tected — in Petromyzon Planeri. In young larvae, bud-like proliferations, 
quite similar to those in Elasmobranchs, arise from all the seven branchial 
sacs. But while in Elasmobranchs and other fishes such proliferations 
arise only on the dorsal commissures of the clefts, and are bilaterally 
symmetrical only on the median sagittal plane, there are in Ammoccetes 
ventral rudiments, and the two sets are symmetrically disposed to a 
median plane. While the maximum number hitherto has been 14 (in 
Heptanclms'), there are 28 rudiments in the lamprey. 
Maturation and Fecundation of the Egg in Amphioxus.* — Dr. 0. 
Van der Stricht has been investigating this subject, but finds, like others, 
that the material is not suitable for the study of minute histological 
details. The eggs were mostly fixed in Flemming’s or Hermann’s solu- 
tions, and stained with safranin. Contrary to the statements of Hatschek 
and Sobotta, the author finds that two polar bodies are formed, one before 
and one after the laying of the eggs. Polyspermy, resulting in the 
formation of several male pronuclei and of subsequent abnormalities, is 
of frequent occurrence. Appearances very similar to those produced by 
polyspermy are frequently found in ova from the peribranchial chamber 
and from the substance of the ovary. In view of the difficulty of 
supposing that spermatozoa can have reached such ova, the author is 
inclined to believe that a partlienogenetic division of the germinal vesicle 
or of the female pronucleus may take place, the vitellus in such cases 
remaining undivided. 
/3. Histology. 
Amoeboid Movements in the Neurodendrites.f — Herr A. von 
Kolliker criticises the hypothesis put forward recently by Duval, aud 
previously suggested by Rabl-Riickhard, that the ends of the neuroden- 
drites are amoeboid, and that this character is of great importance in the 
occurrence of psychical phenomena. While admitting that the hypo- 
thesis appears to throw light upon some phenomena, Kolliker opposes it 
because of the absence of experimental proof, as well as on account of 
the character of the axis-cylinder, which is not contractile and not 
composed of simple protoplasm. Kolliker considers that at present 
there is conclusive evidence that the nerve-cells are the structures 
essentially associated with psychical phenomena, although the neuro- 
dentrites with all their ramifications also play their part. 
Rohon’s Cells in the Spinal Cord of the Trout. J — M. A. van 
Gehuchten has been studying in embryos of Trutta fario the large nerve- 
cells usually called after their discoverer Rohon, which have been de- 
scribed by various authors. By applying the method of Golgi he lias 
obtained preparations showing these cells very clearly. He finds that 
they are pyriform, unipolar, and furnished with a single prolonged pro- 
cess. This process subsequently divides into two, of which the more 
slender remains within the medulla, while the other enters the posterior 
root of a nerve and becomes the axis-cylinder of a peripheral fibre. A 
critical account of the literature of the subject is included, and in an 
appendix the cells are compared to those described by Kutschin and 
Freud in the spinal cord of Cyclostomes. 
* Bull. Acad. Belgique, xxx. (1895) pp. 539-70 (2 pis.), 
f SB. Phys.-Med. Gesell. Wurzburg, 1895, pp. 38-42. 
j Bull. Acad. Belgique, xxx. (1895) pp. 495-519 (7 figs.). 
