THE VITAL PROPERTIES OF THE CELL 307 



a common mother-cell or from the same highly differentiated 

 multicellular mother-organism. Lower Algae, Infusoria, Phanero- 

 gamia and all hermaphrodite animals supply us with a large 

 number of examples of this. 



In Acetabularia, sexual reproduction takes place in such a 

 manner, that swarm-spores are derived in very great numbers 

 from the contents of resting-spores. According to Strasburger 

 and de Bary, conjugation only takes place between two swarm- 

 spores if they are descended from two different resting-spores, 

 whilst those that are derived from the same parent avoid each 

 other. 



Strasburger (VII. 38) says : " About mid-day I saw "two 

 neighbouring spores, which were absolutely indistinguishable 

 from one another, rupture under my eyes, and the swarm-spores 

 of both hurry straight to that edge of the drop which was 

 nearest the window. Soon an extraordinary sight presented 

 itself. I observed that the swarm- spores, which were derived 

 from the same resting- spore, kept at equal distances from one 

 another and evidently avoided each other, whilst at the same 

 time conjugation groups, if I may use the expression, that 

 is to say, heaped-up collections of conjugating-spores, were 

 formed, into which the individual swarm-spores, as it were, 

 precipitated themselves. From these conjugation centres, pairs 

 of united swarm-spores were continually hurrying away." 



In his investigations upon Infusoria, Maupas (VII. 30), by 

 means of several hundred experiments on four different species 

 (Leucophrys, Onychodromus, Stylonichia, Loxophyllum) , has estab- 

 lished the fact, that even when fertilisation is necessary con- 

 jugation only takes place, when individuals of different generation 

 cycles are brought together. 



Maupas remarks : " In many pure cultures of nearly related 

 individuals, the fast, to which I subjected them, resulted either in 

 their becoming encysted, or in their dying of hunger. 



" It was not until after senile degeneration had already begun to 

 make inroads in the culture that I noticed that the conjugation 

 of nearly related individuals occurred in the experimental cultiva- 

 tions. However, all such conjugations ended with the death of 

 the Infusoria, which had paired, but which were unable to develop 

 further, or to reorganise themselves after they had fused. Such 

 pairings are, therefore, pathological phenomena due to senile 

 degeneration." 



