ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 41 



takes place later, when the daughter-chromosomes (i.e. somatic chromo- 

 somes) separate towards the two poles. 



D. M. Mottier * has also investigated this division in Podophyllum 

 peltatum. He now gives up his earlier view that a longitudinal fission 

 occurs for each mitosis, and describes for this form bivalent chromosomes 

 which are produced by the approximation of serially distinct parts of the 

 spireme, each half being, however, double from the early longitudinal 

 fission of the spireme. This work is thus a confirmation of the view 

 as to the nature of this division put forward by Farmer and Moore and 

 by Strasburger. 



Karyokinesis in the Ascomycetes.f — A. Guilliermond returns to 

 this subject, studying anew the plants already examined by him and by 

 R. Maire. He finds himself in accord with Maire as regards the process 

 of mitosis which precedes the formation of spores in Galactinia svccoxa. 

 He found, in the first division he noted, the massing of the chromatin 

 at one side of the nucleus in the synapsis stage, and the appearance of 

 the protochromosomes which develop into 4 chromosomes. Spindle and 

 centrosomes have an intranuclear origin. The asters are partly intra- 

 nuclear and aid in forming the spindle, and they are partly derived from 

 the cytoplasm of the cell. The single centrosome divides, and the two 

 daughter-centrosomes move apart till they are placed opposite each other. 

 At this stage the 4 chromosomes of the equatorial plate divide into 8 ; then 

 a second stage was seen where 8 or a larger number could be counted on the 

 spindle, and at the poles in the anaphase stage 4, 6, or <S chromosomes 

 were counted. The author agrees with Maire that this first division is 

 heterotypic, the second and third, in which the number of chromosomes 

 was invariably 4 on the equatorial plate and 4 at the poles, may be 

 regarded as homotypic. 



The development of the ascus was followed in similar detail in 

 Pustularia vesiculosa and Aleuria cerea, in both of which the number of 

 chromosomes was determined as 8 or about 8 in all the divisions 

 examined (Maire determined them as 4 only). In Peziza rutilans were 

 found 16 chromosomes in the first division massed at the centre of the 

 nucleus ; two centrosomes make their appearance at the same time, and 

 from them radiate the fibres of the spindle. At the poles 16 chromo- 

 somes were also counted in the anaphase stage. The karyokinesis of 

 this form resembles that of other Ascomycetes in the prolonged persist- 

 ence of the nuclear membrane, the intranuclear formation of the spindle, 

 etc. etc. The author gives an account of the presence of metachromatic 

 corpuscles, and basophil granules in the cells. 



Studies on the Plant Cell 4 — B. M. Davis, in the eighth and con- 

 cluding paper in this series, deals with the simplest types of plant cells, 

 and compares them with cells exhibiting higher types of organisation. 

 Other topics discussed are some apparent tendencies in the evolution of 

 mitotic phenomena ; the essential structures of the plant cell and their 

 behaviour in ontogeny ; and the balance of nuclear and cytoplasmic 

 activities in the cell. 



* Bot. Gazette, xl. (1905) pp. 171-7. 



t Ann. MycoL, iii. (1905) pp. 343-61 (3 pis.). 



% Amer. Nat., xxxix. (1905) pp. 695-740. 



