ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
21 
ously been recorded. It is a form of double monstrosity, in which one 
of the two individuals is parasitic on the other, and in which the parasite 
has a distinct head, and at least rudimentary pelvic limbs. He discusses 
the various theories as to such phenomena, and inclines to believe that 
the two forms result from one ovum with two nuclei, of which one has 
been fertilised, while the other has developed parthenogenetically. 
Structure and Development of the Vertebrate Brain.* * * § — Prof. B. 
Haller has made a detailed study of the brains of Salmo and Scylliiim, 
and discusses the Vertebrate brain in general. We cannot attempt to 
summarise his results, which extend over nearly three hundred pages, 
but w r e may give a hint as to his speculative conclusion, which cannot be 
said to lack solid basis. The primitive form of the Chordata (the Hel- 
minth) had as a central nervous system a pair of supra-cesopkageal 
ganglia and lateral nerve-cords. The two cords approached one another 
dorsally and coalesced in a single dorsal cord. Their former separate- 
ness remained only in the central canal, which was continued on to the 
primitive brain, where a similar cavity arose by a coalescence of the 
ventral parts of the ganglia. The two cavities communicated directly. 
Thereafter began a metameric differentiation of the nerves, both cerebral 
and spinal. On the pre-chordal brain, the formation of the Vertebrate 
paired eyes began the process of cerebral differentiation to which the 
subsequent concentration of the olfactory spheres gave a further im- 
pulse. 
b. Histology. 
Experimental Cytology.! — Dr. A. Labbe has done a useful piece of 
work in preparing a handy introduction to experimental cytology. It 
sums up the chief results of recent work on microscopic foams, the in- 
fluence of environment on cell-structure and metabolism, the inter-rela- 
tions of nucleus and cytoplasm, the various “tropisms” and “ tactisms,” 
and so on. There is not a great deal about any one subject, but there is 
a little about many subjects, and all is clear and accurate. 
Formation of Blood-corpuscles in the Lamprey.J — Sig. M. Ascoli 
finds that in the ?amprey the production of both the white blood-cor- 
puscles and the red blood-corpuscles takes place by the mitoses of 
corresponding young stages of these. The mitosis of the leucocytes was 
observed both in the circulation and in the lymphoid tissue of the spiral 
valve and kidneys, while the mitosis of the red blood-corpuscles was 
observed only in the circulation. 
Eosinophilous Granulations of Leucocytes.§ — Dr. N. Bogdanoff 
supports the view, that just as the chromatin substance of the nucleus 
may form in whole or in part “ Lsemoglobinogen ” substance in the red 
blood-corpuscles, so it may be transformed into eosinophilous granula- 
tions, and then into fat in the leucocytes. 
Post-Embryonal History of Striped Muscle-fibres. || — Mr. A. Meek 
has sought an answer to the question whether the fibres are added to 
* Morphol. Jahrb., xxvi. (1898) pp. 345-641 (11 pis. and 23 figs.). 
t ‘La Cytologie expeiimentale. Essai de cytomecanique,’ Paris, 1898, 8vo, viii. 
and 187 pp., 56 figs. J Atti Accad. Fci. Torino, xxxiii. (1898) pp. 916-23. 
§ Physiol. Eusse, i. (1898) pp. 35-43 (2 pis.). 
|| Anat. Anzeig., xiv. (1898) pp. 619-21. 
