by r. von lendekfeld, ph.d. 549 



Histology. 



The study of some well preserved specimens of this sponge has 

 led to some interesting discoveries, which show that this species 

 possesses some peculiarities in its structure hitherto not observed in 

 other sponges. 



Gland Cells. 



In the skin between the canals, which lead down from the pores, 

 amoeboid cells are found, which present the usual shape, but appear 

 more granular. Others again with a still more granular protoplasms 

 are found attached to the ectoderm cells covering the outer surface 

 and the inhalent canals. 



There are all desirable transition forms from these amoeboid 

 wandei'ing cells to true gland cells (Plate XXXVIII., fig. 2 a) 

 attached by their thin end to the ectodermal epithelia. These are 

 club-shaped and resemble those gland cells described by Merejowsky 

 (1) of Halisarca very closely. They differ from those described by 

 me of Aplysillidaj (2) only in so far as they possess only a single 

 process to connect them with the surface. 



No nucleus is visible in these cells, which are completely filled 

 with granules when fully developed. 



The remarkable thing is, that these cells are found not only on 

 the outer surface but all along the narrow inhalent canals. 



It makes one the impression that some of the amgeboid wander- 

 ing cells are converted into these gland cells, wherever these gland 

 cells may be required. The whole of the protoplasm of the 

 amoeboid cells seems to be converted into the slimy secretion, the 



It is further of interest to note that these gland cells are 

 expelled from the sponge in toto, and that they then spread out on 

 the outer surface where apparently they are converted into slime. 



(1) C. Merejlcoicslcy. Etudes sur les- Esponges de la Mer Blanche. 

 Mt^moires de rAcademie Imperiale des Sciences de St. P6tersbourg, VII. 

 Serie, No. 7. 



(2) R. von Lendenfeld. Ueber Ccelenteraten der Siidsee. II. Mittheilung. 

 Neue Aplysinidse. Zeitschrift fiir wissenachaftliche Zoologie. Band 

 XXXVIII., Seite 268. 



