THE BREEDING SEASON 9 



the process every morning for a number of weeks, when the 

 breeding season comes to an end. In one season, when the 

 aquaria were somewhat neglected, the specimens of Sagartia 

 produced fewer young than usual, and these were not extruded 

 until the beginning of April. Specimens of Actinia Hving in 

 the same aquaria were more proKfic, but their breeding season 

 was also somewhat retarded. In the month of August two 

 anemones of the species Sagartia troglodytes were brought from 

 Thorshavn in the Faeroes, and placed in the aquaria. In the 

 following October both of these produced several young ; while 

 in April of the next year one of them again gave birth, but only 

 to a single anemone. It seems probable that in this case the 

 change of temperature or environment had induced the anemones 

 to breed at an unusual season ; for it is unlikely that October 

 is the normal period for reproduction in the Faeroes, as by this 

 time the sea has already begun to run high, and there would be 

 a great risk of the young anemones becoming destroyed, being 

 unable to attach themselves. 



Ashworth has pointed out ^ that in the coral Xenia hick- 

 soni, which hves in the tropics, there is every evidence that 

 spermatozoa are discharged over a very considerable period, 

 if not practically throughout the whole year, whereas in the 

 related form Ahyonium digitatum, of Northern Europe, the 

 period during which the spermatozoa are discharged is hmited 

 to about a month in the winter. Ashworth remarks that the 

 difference is probably due to the fact that Xenia, living on 

 reefs in the shallow waters of tropical seas, is not subject to 

 great variations in temperature and food-supply, while with 

 Ahyonium, such variations are no doubt considerable. In a 

 similar way Miss Pratt,^ who has studied the process of oogenesis 

 in Sarcofhytum, Holo-phytum, and Sclerophytum, concludes that 

 the sexually mature condition in these tropical genera extends 

 over a considerably longer period than in the case of corals 

 inhabiting temperate waters. 



It may also be noted that, whereas in the Ctenophora of 

 the Mediterranean the breeding season extends throughout the 



' Ashworth, " Structure of Xenia hicksoni," Quar, Jour. Micr. Science, 

 vol. xlii. 



* Pratt, " On Some Aloyonidas," Berdman's Ceylon Reports, vol. iii. 



