476 LIFE : OUTLINES OF GENERAL BIOLOGY 



breeding season there is spawning. Thereafter a fresh crop of genital 

 products is developed, to be spawned at the ensuing full moon. One 

 and the same individual may become sexually mature at consecutive 

 lunar periods. Another sea-urchin (Strongy<locentrotus lividns) was 

 observed at Alexandria, Naples, Marseilles, and Roscoff, but it 

 showed no lunar periodicity. 



It is difficult to suggest how the lunar changes can affect the 

 sea-urchin Centrcchinus in times of spawning at Suez. Mr. Fox 

 has found that the oxygen-consumption of pigmented animal 

 tissues is greater in light than in darkness, and he suggests that if 

 moonlight has sufficient intensity to cause this effect, this may be 

 the reason for the lunar periodicity in the spawning of the Suez sea- 

 urchin. This clue is being followed. 



E.NDOMixis. — For eight years or more Prof. L. L. Woodruff, of 

 Yale, has been able to keep agoing a "pure line" of Paramotcium, 

 all descended from one by asexual fission, continued for hundreds 

 of generations. In such a "pure line" there is no conjugation such 

 as has been already described. But, while conjugation does not 

 occur, Prof. Woodruff and Miss* Erdmann discovered that there is 

 a monthly occurrence of a remarkable process which they have called 

 "endomixis". In this process, which is like the prelude to con- 

 jugation, the nuclear apparatus is scrapped and then reorganised. 

 It seems to have a rejuvenating effect. 



It seems that both conjugation and endomixis are able to meet 

 the emergency of physiological degeneration, which may be 

 induced, for instance, by deteriorative environmental conditions. 

 The process of endomixis was discovered in an artificially isolated 

 "pure line", but Woodruff has found that it also occurs in free 

 natural conditions in the species Paramcecium aurelia and P. cauda- 

 turn, and it is surely not without significance that these two species 

 are very widespread and are able to exist under very diverse 

 environmental conditions. They have got possession of a secret of 

 rejuvenation— which seems to be in its external aspects like scrapping 

 the organisation and reconstructing it afresh. 



How Sperm.mozo.a Reach the Ova. — Here is one of the simplest 

 of questions: how it is that spermatozoa, introduced by the male 

 into the lower part of the female genital tract, manage to make 

 their way to the upper part of the oviduct, such as the Fallopian 

 tube. It was in 1843 that Martin Barry, a medical student in Edin- 

 burgh, was first able to demonstrate for a mammal (the rabbit) 

 the fertilisation of the ovum by a spermatozoon within the oviduct, 

 but how the spermatozoa reach the ova is still obscure. The interior 

 surface of the female duct is lined with cilia, which beat vigorously 

 towards the distal end, and are reasonably believed to assist in the 

 downward passage of the egg-cell, in a bird, for instance. But if 



