410 H. BOSCHMA. 



decalcifying the specimens, in other colonies only sparsely dis- 

 tributed threads are to be found. In an allied species, Astrangia 

 solitaria, the skeleton is also penetrated by boring algae (Duerden, 

 1902). Besides these boring forms there is another alga which 

 lives in the tissue of the polyps. Mrs. Dr. A. Weber van Bosse, 

 who kindly examined the preserved material of these algae, found 

 that it represents a new species of the genus Streblonema. 1 



For different reasons the polyps of Astrangia are -especially fit 

 objects for the study of their feeding habits. During the daytime 

 they are usually fairly well expanded. 2 After being disturbed the 

 polyps contract within the skeleton, but usually they will expand 

 again in a very short time after the disturbance. Even when 

 they are transferred from one glass-vessel to another they soon 

 .return to their expanded state. One of the further advantages of 

 Astrangia in my experiments was that the polyps will ingest 

 almost every particle which is offered to them, as well food as non- 

 nutrient objects. 



All the polyps of freshly-collected colonies of Astrangia dance do 

 not react in quite the same way on a certain stimulus, probably 

 on account of the disturbance caused when they are collected. 

 When, however, the colonies have been a few days in the labora- 

 tory under constant external influences they constitute a fairly 

 uniform material for feeding experiments. Especially more or 



1 1 am indebted to Mrs. Dr. A. Weber van Bosse for the following diagnosis of 

 this interesting form: 

 "Streblonema Willy ae n. sp. 



Frondibus microscopicis in telum Astrangiae danae penetrantibus, compositis e 

 filamentis sterilibus, irregulariter alterne aut secundatis ramosis, 2-5 /j. latis, 

 aggregatis, fascicules prope superficiem hospitis formantibus. Chromatophoris 

 taeniatis aut disciformibus, parietem cellulae non totius tegentibus. Sporangiis 

 ignotis. Gametangiis cylindricis aut fusiformibus, singulis aut ramosis in filamentis 

 plerumque terminalibus, interdum lateralibus, longis 60-120 ju, latis 8-iOju; loculis 

 uni- et pluriseriatis. Pilis desunt. 



This new species of Streblonema is so far interesting as it grows in a coral, not in 

 the skeleton but in the soft tissue of the animal. It has this mode of living in an 

 animal in common with the genus Endodictyon, but the apical and above all the 

 branched gametangia seem to indicate that its proper place is in the genus 

 Streblonema." 



2 It is a well-known fact that the greater part of the madreporarian coral polyps 

 are nearly always found in a contracted state during the day-time. Besides 

 Astrangia there are, however, exceptions on this rule, e.g., the polyps of Fungia t 

 Goniopora and Euphyllia from the East Indian coral reefs, which are during daytime 

 in a fully expanded state. 



