Studies on Synapsis. 



75 



cell constituents, concluded that the double nucleolus is formed by the 

 condensation of the synaptic spireme around the plasmosome during maximal 

 contraction. But complicated methods of differential staining cannot suffice 

 to shed light on cell problems, unless proper attention is paid concurrently to 

 the technique of fixation ; and McGill's materials were entirely fixed in fluids 

 containing acetic acid. As a matter of fact, the plasmosome is uniformly 

 fuchsinophil after fixation with Flemming's modified formula (Gatenby), i.e., 

 unless rendered basophil by previous treatment with acetic acid ; this is true 

 of all stages in oogenesis, both for Libellula and Periplaneta. There is no 

 need to recapitulate previous comment (Qi, pp. 315-319) on the value of 

 differential staining ; the conclusions built up within the scaffolding of the^ 

 now discarded binuclearity hypothesis indicate the sources of error that arise 

 from data derived in this way only. 



Having examined living material in Libellula, it is possible to state with 

 greater confidence what occurs in the nucleus during the diffuse stage. At 

 the inception of the period of growth, after fixation in Flemming's, Bouin's, or 

 Tellyesnicsky's fluids, the plasmosome, which undergoes at this time rapid 

 increase in size, is seen to have changed its staining reaction. This may merely 

 be a physical consequence of increase in surface (c/. Fischer's granules) ; and 

 does not necessarily denote alteration of chemical constitution. Intranucleolar 

 vacuoles make their appearance and increase in volume one at a time, each 

 one successively enlarging, until it occupies the greater part of the plasmo- 

 some, while simultaneously becoming oxyphil in its reaction. Thus the 

 apparent double nature of the plasmosome results not from the absorption of any 

 part of the chromatinic organisation of the nucleus, but from a process of 

 internal differentiation. 



The only difference between the behaviour of the plasmosome in the 

 oocytes of Libellula and Periplaneta in this respect is that the vacuolar bodies 

 within the nucleolus attain their full size singly in the former, whereas 

 several mature at a time in the latter. Their subsequent fate is similar in 

 both genera. Each of these vacuolar bodies, which for ulterior reasons as 

 well as to avoid the confusion between chromatin, mitochondrial, and 

 nucleolar substance suggested by the older term " chromidia " have been 

 designated deutosomes (6), emerge from the plasmosome into the karyolymph. 

 According to McGill in the case of Anax and Plathemis they dissolve in the 

 karyolymph ; but in preparations made with the mitochondrial technique of 

 Gatenby and Kopseh they are found to pass out into the cytoplasm to the 

 periphery of the egg, where they eventually break up into smaller spheres 

 which become the first vitellus (fig. 39). 



Since the nuclear origin of the mitochondria has been discredited, cyto- 



VOL. xcii — B. . G 



