138 ZOOLOGY 



which is deeply staining. These disappear, and the plasmosome 

 is seen to contain vacuoles. These vacuoles are in turn emitted 

 and new vacuoles formed, which follow the others into the 

 cytoplasm. These vacuoles are termed by Hogben deutosomes, 

 as they become yolk. 



In Libellula depressa the nucleolus is differentiated into two 

 concentric regions (Fig. 62, C). Intranucleolar vacuoles make 

 their appearance during the growth phase one at a time and 

 emerge first into the nucleus and then into the cytoplasm, where 

 they pass to the periphery, break up and form yolk. They thus 

 are deutosomes. 



Ludford, in Patella (75), describes a very complicated process 

 of nucleolar extrusions which apparently result in part in the 

 formation of yolk. The nucleolus is here definitely differentiated 

 into two parts which lie, separated eventually from each other, in the 

 nucleus (Fig. 62, D-F). One part is oxyphil, the other basophil. 

 E:?^rusions continue during the differentiation, particularly from 

 the increasingly basophil part. The oxyphil portion dwindles and 

 fragments, and is ultimately extruded into the cytoplasm, where 

 it is apparently related to yolk formation (Fig. 62, D-H). The 

 basophil portion fragments, the granules becoming attached (?) 

 to the lignin network (Fig. 62, G, H). 



The almost classical case of nucleolar emissions is described by 

 Gatenby in the case of Saccocirrus (Fig. 62, A, B) (33). Nucleolar 

 extrusions commence at an early stage and continue throughout 

 the oocyte. The extruded portions remain attached to the nuclear 

 membrane, where they undergo differentiation, becoming the centre 

 of vacuoles inside of which the nucleolar granules partially break 

 up. On the absorption of the vacuoles the granules are scattered 

 throughout the egg as deutoplasm (Fig. 62, B). " The deutoplasm 

 forms dense clouds of heavy granules throughout the entire egg 

 cytoplasm." 



Gardiner (29) states that there are definite nucleolar extrusions 

 in the oogenesis of Limulus polyphemus, and that with the help 

 and interaction of chondriosomes, dictyosomes and ground dyto- 

 plasm, yolk is formed. However vague this account, it does 

 connect the extrusions with yolk formation. Both King (69) and 



