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Type D. represented by L. veutricosa (Crtr.) Dd. Here we find 

 again a complex of Ascon-tubes and a pseudoderm. But the in- 

 side of the main exhalant tube, terminatiug into the »osculum" 

 is not lined by choanocytes. A great portion of this »pseudogas- 

 ter" is lined by pinacocytes. The author believes these cells to 

 be ectodermal, and considers the »pseudogaster" as lying „out- 

 side the colony and formed probably by the upgrowth of the co- 

 lony around it". Accordingly the openings of the Ascon-tubes in 

 this pseudogaster are considered to be the ))true oscula". 



Type E. represented by L. proxima Dd. The central cavities 

 of the Ascon-tubes more or less subdivided into incomplete cham- 

 bers by ingrowth of xmesoderm" which is not lined by choanocytes. 



Type F. represented by L. wilsoni Dd. A further developementof E.; 

 the ingrowths are more strongly developed and lined by choanocytes. 



3. Radiata. The colony consists of a central tube from which 

 smaller tubes are budded radially. This is found in L. tripodifera 

 (Crtr.) Dd. The whole sponge resembles a sack , the thick walls 

 of which are made up by a great number of radial tubes. At 

 the top is a wide „osculum" and here there are no radial tubes, 

 the wall being thin and perforated by pores. At a short distance 

 below the osculum , however , small buds are visible ; lower down 

 these buds are longer and ramify ; they ofter touch and there is 

 sometimes a communication between them. The whole central ca- 

 vity is lined by choanocytes. 



II. The morphological value of the ierms osculum 

 and pore in sponges. 



The words osculum and pore are used for things, which are 

 by no means homologous , nor do spongiologists attach the same 

 meaning to these terms. Although no proof can be given as long 

 as we do not know more about the ontogeny of sponges, we 

 still know by anatomical observations that in certain cases evid- 

 ently different formations are called osculum or pore. I will 

 therefore attempt to define more strictly what we may call osculum 

 etc. in various sponges and what decidedly not. 



