IK.8A 



] ^otes 



89 



base of thezooeciatlie latter are pressed together and become elon- 

 gated in proportion to the extent to which thej are buried. If 

 the aperture were not on the external surface of the Sponge, the 

 polypide would be unable to expand its tentacles and so would 

 perish for want of food. The relationship between the Sponge and 

 the Polyzoon, although it occurs very commonly, is a casual one, 

 probably beneficial rather to the Sponge, as giving it additional 

 support, than to the other organism. Some of the largest examples 

 of Spongilla carteri I have found have been permeated by colonies 

 of P. repens (coralloides) , the zooecia oi which had reached a gi'eat 

 length before undergoing division, but had bifurcated many times 

 over on the outside of the sponge without ever extending much 

 beyond it. In smaller specimens the tubes are frequently simple 

 or have only branched to a slight extent. 



P, repens, as far as Calcutta is concerned, occurs most com- 

 monly, if not only during the rains and in winter. Under natural 

 conditions it does" not appear to be very prolific of statoblasts in 

 this locality; but if a colony is kept in a glass of water it soon 

 produces both floating and sessile forms in considerable abundance. 

 In the tanks these bodies appear to be more numerous towards the 

 end of the rains and at the beginning of the hot weather than 

 during the intervening cool season. I have often found P. repens 

 and P. emaratnata orowinor tos^ether on the same brick or plant. 



Plumatella E3IARGINATA, Allman- 



P. emarginata and stricta, Allman, pp. 99, 104, pi. yii^ figs. 

 5-10 ; P. princeps mr, emarginata, Kraepelin, p. 120, pi. iv, figs. 

 108; pi. V, fig. 123; Alcyonella benedeni, id., p. 119, pi, iv, fig. 

 113. 



The only difference between P. emarginata and P. stricta is that 

 the latter has no furrow and keel on the zooecia. 1 find every vai-ia- 

 tion between a well developed furrow and keel and complete absence 

 of both these features in specimens from Calcutta ; indeed, they are 

 not equally developed, in some cases, on all the zooecia of the 

 same colonj. Eegarding the two forms as identical, P. emar- 

 ginata may be recognized by its densely pigmented zooecia with 

 their pale distal zone, and by the more or less elongated form of 

 its statoblasts. The diameter of the tubes is generally smaller 

 than is the case with P. repens, but their walls are stouter. When 

 the two species are groyning together the contrast between them is 

 very striking even to the naked eye. Agglutinated colonies with 

 parallel, vertical tubes (Alcyonella henedenh^ .Ulman) often occur 

 together with the more diffuse phase during the winter months. 



Carter has recorded P. stricta from Bombay Both forms are 

 common in the Calcutta tanks on floating sticks and submerged 

 bricks. I have found statoblasts closely resembling those of the 



Plumatella 



A otncciy speaking t/ne Hpu^^iut? <««*...« »»- 



Alcyonella beiiedeni waa described hetote Plumatella emarginata. 



