130 Transactions of the Society. 



One of the most remarkable cases of nucleclar extrusion is 

 that which has been described in Hymenoptera by Buchner {3), 

 Hegner (see 6), and Gatenby {6). In t]ie oocyte of certain 

 Hymenoptera, the nucleolus buds off bodies which pass out of the 

 nucleus into the cytoplasm, where they give rise to " secondary 

 nucleoli" with a basophil reticulum and an oxyphil nucleolus. 

 The function of such " secondary nucleoli " is not properly known. 



The behaviour of the basophil nucleolus of the Patella oocyte 

 is paralleled by that of Daphnia 'puUx worked out by Kuhn {10), 

 and I have observed exactly the same process occurring with the 

 basophil nucleolus of Limnaia. The large central nucleolus in the 

 oocyte of these organisms towards the end of oogenesis becomes 

 vacuolated and breaks up to form a mass of granules which spread 

 over the linin network, as in Patella. Kuhn found that with the 

 reappearance of the chromosomes, preparatory to the maturation 

 divisions, the greater part of the nuclear matter disintegrated. 

 Lack of suitable material has so far prevented the observation of 

 the later stages in Patella, but the problem is still being 

 investigated. 



Marechal found a process of disintegration of the nucleolus of 

 a somewhat similar nature in the oocytes of Selachians (1'^) towards 

 the end of oogenesis. When the chromosomes were reforming, the 

 nucleolus broke up into a mass of granules which became scattered 

 in the nucleus, and in some cases formed rodlets resembling the 

 chromosomes. 



It is very difficult to find any explanation of the function of 

 the nucleolus in such cases as these. In Patella and Limiwea. the 

 basophil nucleolus is undoubtedly a specially elaborated substance, 

 and it seems to me possible that it stands in some functional 

 relationship to the subsequent condensation of the chromosomes 

 as compact rodlets out of the diffused chromatinic reticulum. 

 Possibly this is effected by producing a shrinkage or contraction of 

 the framework upon which the cliromatin is distributed, or may be 

 by a kind of flocculation. 



This is borne out by the fact that in preparations of the 

 ovotestis of Limnxa which I have studied, there is a marked 

 elaboration of basophil substance in the oocytes, and towards the 

 end of oogenesis, the basophil body disintegrates and spreads over 

 the linin reticulum, as in Patella. In the spermatocytes, however, 

 there is an amphinucleolus with definite oxyphil preponderance, 

 which is present in the cells up to the late synaptic stages of the 

 heterotypic prophase. There is no elaboration of definite basophil 

 substance, nor is there any extrusion of nucleolar material during 

 spermatogenesis. 



Eecent work on staininsr reactions has shown that we have no 

 stain which can be relied upon as a criterion for chromatin. 

 In preparations of the ovotestis of Limnxa stagnalis fixed in 



