222 SCIENCE PROGRESS 



They do, however, divide and spread throughout the cyto- 

 plasm during growth of the oocyte. The formation of yolk 

 is essentially the function of the nucleolus, which buds off 

 fragments into the cytoplasm and these lead to the formation 

 of yolk spheres. 



The behaviour of the cytoplasmic organs during spermato- 

 genesis is similar in many respects to that in other organisms 

 which have been studied. The mitochondria, however, fuse 

 in the spermatid and later form the tail sheath, but the Golgi 

 apparatus is possibly sloughed off. It may, however, be 

 represented in the mature germ cell by granules which occur 

 on the distal end of the tail. The tail of the sperm penetrates 

 the egg at fertilisation, but Gatenby does not consider that 

 these " tail granules " have any functional significance. 



The probable part played by the cytoplasmic inclusions in 

 inheritance is discussed in the same paper. 



Since Montgomery's classical paper on the nucleolus was 

 published in 1895, a large number of papers have appeared 

 dealing with the structure and function of this cell organ. A 

 critical survey of the new work is given by R. J. Ludford in 

 the Journ. Royal Micr. Soc, June 1922 (" The Morphology 

 and Physiology of the Nucleolus," Pt. i). The same paper 

 also contains an account of the behaviour of the nucleolus in 

 the germ cell cycle of the Mollusc, Lijnncea stagnalis. Nucleolar 

 extrusions are described during oogenesis, and in somatic cells 

 during periods of special metabolic activity. The probabihty 

 of the nucleolus having a special nutritional function in the 

 cell is emphasised. 



Other papers include : 



(i) " Der Fettkorper und die Oenocyten von Dytiscus marginalis," by 

 Arthur Kreuscher [Zeif. fiir Wiss. ZooL, April 1922). Of special interest 

 are the oenocytes, which have a system of fine secretory canaliculi extending 

 from the nucleus radially to the periphery of the cell. " Es sind Zellen mit 

 innerer Secretin." 



(ii) " Beitrage zum feineren Bau der Purkinje' schen Fasern im Herzen 

 der Vogel," by E. H. Tang [Anat. Anz., 55 Band, Nr. 16, 17), in which is 

 described the cytoplasmic organs of the cells of the " Purkinje' schen 

 Fasern " — granular mitochondria, circum-nuclear Golgi apparatus and 

 myofibrillae. 



(iii) " The Behaviour of the Golgi Bodies during nuclear division, with 

 special reference to Amitosis in Dytiscus marginalis," by R. J. Ludford 

 {Q.J. M.S., vol. Ixvi, No. 261, March 1922). 



Histology. — " Histogenese et regeneration du muscle chez 

 les Anoures " is the subject of a paper by Andre Naville in 

 the Archives de Biologie, April 1922. He points out that 

 muscle fibres are formed of two parts, which are quite distinct 

 with regard to their potentialities. There is the sarcoplasmic 

 part containing numerous mitochondria and nuclei, and there 



