ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 437 



b. Histology. 



What are Plastosomes ?— Fr. Meves* answers some criticisms by 

 Retzius, who doubts the distinctiveness of plastosomes or chondrio- 

 somes. The answer to the question, What are plastosomes ? is some- 

 what as follows. The plastosomes are granules or threads of a specific 

 nature, which are often visible in the living cell ; they are present in all 

 embryonic cells and in many cells of the adult body ; they lie between 

 the radiations or mitom of the cytoplasm, or between the threads of 

 the framework which takes the place of the radiations ; they are dissolved 

 by strong acids or by strongly acid fixatives ; they can be isolated 

 microscopically, more or less perfectly, by using certain methods 

 (Altmann, Benda, Meves, Rcgaud, and others) ; they pass in mitosis 

 from the mother-cell to the daughter-cells ; they represent according to 

 many the primordial material for the most diverse differentiations that 

 occur in development ; male plastosomes pass with the sperm into the 

 ovum at fertilization. 



Dimensions of Chromosomes.f— C. F. U. Meek found some evidence 

 in 1912 that both the diameter of the chromosome rods and the total 

 volume of chromatin on the spindles increase as we pass from less to 

 more complex organisms. He has lately studied the spermatogenetic 

 mitoses of Smerinthus populi and Gallus domesticus. In the former, 

 both the diameters of the chromosomes and the total volume of chro- 

 matin on the spindles are noticeably smaller than those observed in 

 corresponding cell-generations of organisms of similar or even inferior 

 somatic complexity. In the latter, the chromosomes are closely crowded 

 on the spindles, and accurate measurement of the rod diameters is 

 therefore difficult ; but no doubt can exist that the total volume of 

 the chromatin present is considerably less than that found in Steno- 

 bothrus and Helix, and many other lower organisms. 



It seems, then, that neither the diameter of the chromosome rods 

 nor the total volume of chromatin on the spindle can be correlated with 

 the degree of somatic complexity of the organism. Thus cytometrical 

 investigations have yielded only negative generalizations. The author 

 proposes to continue his investigation. If his final results are also 

 negative, it will show that this line of enquiry is unprofitable. 



Movement of Chromosomes in Nuclear Division.^ — Richard 

 Geigel has given special attention to the movement of the daughter- 

 chromosomes from the equator toward the centrosomes, and considers 

 the mechanical interpretation proposed by Hartog. Geigel finds him- 

 self compelled to assume a special ; ' vital attraction " or " vital force 

 from a distance " — something peculiar to protoplasm. 



Transformations and Excitability of Protoplasm. § — R. Demoll 

 has made a number of experiments with the liver-cells of newts which 



* Arch. Mikr. Anat., lxxxv. (1914) lte Abt., pp. 279-302 (17 figs.). 

 t Note from C. P. U. Meek, Culls, Stroud, Gloucestershire, pp. 1-3. 

 t Arch. Mikr. Anat., lxxxiv. (1914) pp. 453-64 (2 figs.). 

 § Zool. Jahrb. Abt. Allg. Zool., xxxiv. (1914) pp. 543-58 (12 figs.). 



