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Australian waters. One point clearly demonstrated is that 

 copulation can only take place under conditions in which the 

 respective individuals are qualified for copulation. These condi- 

 tions are apparently determined by the state of the nucleus. 

 Copulation only ensues when the individuals concerned have but 

 a single nucleus and this nucleus at rest, that is to say, not 

 undergoing sub-division. In every case observed where one or 

 both of the individuals of the same species had their nuclei on 

 the way to divide, the pseudopodia instead of fusing shrank away 

 from each other, but when two individuals approached each other 

 having their nuclei in the embryonic chamber, in a quiescent 

 condition, copulation ensued. These results were observed, not 

 only in the case of such examples as happened to come into contact 

 fortuitously, but were repeatedly experimentally confirmed by 

 Schaudinn, who used artificial means in bringing individuals to- 

 gether in various states with regard to their nuclear condition. 



The act of copulation in the case of Patellina consists ap- 

 parently in the fusion of the protoplasm — that is, the cytoplast as 

 distinct from the nucleus in the individuals concerned. First the 

 pseudopodial extensions touch and merge and ultimately the main 

 portions blend, by which means the respective tests are raised 

 until they touch, not face to face, but at an angle forming a V 

 shaped space between the two shells. The open sides are rapidly 

 built up by the organisms with grains of sand and other fortui- 

 tous fragments that may be at hand, to give the greater protec- 

 tion, and (as we have already seen taken place in the case of 

 Polystomeila crispa when in the act of reproduction) the whole 

 of the animal substance leaves the shells and is united into one 

 mass enclosed within the chamber formed for the occasion. After 

 the lapse of an hour or two, or even days, the protoplasmic mass 

 breaks up and concentrates around the nuclei ; each little frag- 

 ment takes a globular form and secretes a test which forms the 

 embryological chamber of the new life. When the embryos are 

 ready for independent existence the temporary barriers are 

 broken and they escape from the " nuptial cavern." In this act 

 of copulation several individuals can take part concurrently 

 (Schaudinn actually observed groups up to five) but they must all 

 be mononucleary in condition, and the fusion is limited to the 

 protoplasm as distinct from the nuclei. 



The process of copulation in Discorbina is very similar to that 

 already described in the case of Patellina. The Hat faces of the tests 

 are brought together so that the respective apertures can readily 

 communicate. Portions of the walls of the final chambers are even 

 reabsorbed to permit of freer intercourse, and the open space 

 between the shells temporally enclosed by a film of carbonate of 

 lime. The multiplication of the nuclei and the formation of 



