SUMMARY OF CURRENT RESEARCHES 



RELATING TO 



ZOOLOGY AND BOTANY 



(principally invertebrata and cryptogamia), 



MICROSCOPY, Etc.* 



ZOOLOGY. 



VERTEBRATA. 



a. Embryology, t 



Number of Chromosomes. J — Th. Boveri finds that in Echinoids an 

 abnormal number — plus or minus — of chromosomes in an ovum or in a 

 blastomere persists, unless further abnormality sets in, unchanged from 

 one cell-generation to another, on to the gastrula stage, and probably 

 further. There is no regulation restoring the normal number. What 

 was shown to obtain in Ascaris holds good for Echinoids. 



In such cases the chromosomes, abnormal as to their number, have 

 their typical volume, and the size of the nucleus is directly proportionate 

 to the number of chromosomes. The size of the larval cells is a func- 

 tion of the amount of chromatin, and the cell volume is directly propor- 

 tionate to the number of chromosomes. The number of larval cells is 

 inversely proportionate to the amount of chromatin or the number of 

 chromosomes. The proportion of the total protoplasm of a larva to the 

 total mass of chromatin is constant. Given equal amounts of chromatin, 

 the number of larval cells is proportionate to the protoplasm-mass of the 

 egg. By regulating the number of cell-divisions, the organism regulates 

 the proportion of chromatin to protoplasm. Within limits the normality 

 of development is independent of the number of chromosomes. But it 

 is not merely the quantitative mass of chromosomes which has to be 

 considered ; there must be a representation of the different kinds of 

 chromosomes, if there is to be normal development. 



Experiments on Cytoplasm of Amphibian Ovum.§ — A. Gurwitsch 

 has shown the power that the cytoplasm has of reconstituting itself after 



* The Society are not intended to be denoted by the editorial " we," and they 

 do not hold themselves responsible for the views of the authors of the papers noted, 

 nor for any claim to novelty or otherwise made by them. The object of this part of 

 the Journal is to present a summary of the papers as actually published, and to 

 describe and illustrate Instruments, Apparatus, etc., which are either new or have 

 not been previously described in this country. 



t This Section includes not only papers relating to Embryology properly so called, 

 but also those dealing with Evolution, Development, Reproduction, and allied subjects. 



X Jenaische Zeitschr. Naturwiss., xxxix. (1905) pp. 445-524 (2 pis. and 7 figs.). 



§ Verh. Anat. Ges., 1904; Anat. Anzeig., xxv., Erganzungsheft, pp. 146-52 

 <6 figs.). 



