580 Note on Astrosclera willeyana Lister. 



vivens, filiformis, monosiphonius, septatus (rare articulatus), ramosus ; 

 stichidia, tetrasporangia cruciatis tetrasporis prsebita, gerens. 



Color, fere sine dubio, aurantiacus (sensu Saccardoi). 



B. cor-margaritae* n. sp., Diagnosis ut genus. 



A fully illustrated account of the very remarkable life-history of 

 Astrosclera-Rhododiplobia will shortly be published, which, I trust, will 

 furnish clear proof as to the accuracy of the statements here made. The 

 two organisms have become, in all reasonable probability, indispensable to 

 each other and inseparable. The sponge embryos, before they have left the 

 parent, are associated with plants bearing carpogonia antheridia or stichidia, 

 and even the youngest sponges, barely visible to the naked eye, have solid 

 well-built skeletal walls composed of aragonite spherules each with an algal 

 spore in its centre. I consider that the association has become one of true 

 symbiosis, and is not merely an instance of parasitism of the alga on the 

 sponge, or vice versd. 



* Cor, heart ; margarita, pearl. 



ERRATUM. 



Page 141, lines 4 and 6 (from bottom), and p. 142, 2nd column of table, for 

 postometer read potometer. 



