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2. Reticulata. The colony forms a more or less complex network 

 of tubes ; it is no louger possible to distinguish separate iudivi- 

 duals. The author finds six types of the reticulate form of canal 

 system. 



Type A. represented by L. dubia Dd. The colony forms a loose 

 network of tubes , without a common investing skin. 



Type B. represented by L. stipitata Dd. and L. pulcherrima 

 Dd. The colony consists of a network of tubes , which debouch 

 in one or two main tubes. The inside of the whole complex of tubes 

 is lined by choanocytes. The peripheral tubes are generally wider 

 than the interspaces between thera. There is thus formed a kind 

 of common outer wall (»pseudoderm") with inhalant apertures 

 (»pseudopores"). A further remarkable modification is that the 

 strengthening spicules of this »pseudoderm" are ))of somewhat 

 greater size" than those of the central parts of the colony. 



Type C. represented by L. cavata Dd. Here we find a very 

 striking modification of the type B, a part of the canal system 

 being »reversed". The lowermost (older) portion of the colon}' 

 consists of a number of very simple branching and anastomosing 

 tubes. These tubes are narrow , the interspaces between them are 

 wide. There is thus no conspicuous »pseudoderm". In the upper 

 (younger) portion of the colony however, the peripheral tubes fuse 

 and in this way their outer walls form a »pseudoderm", leaving 

 between them small apertures, »pseudopores". At the same time 

 all the tubes increase in diameter and become very irregular, 

 while the interspaces become constricted. The end is that »the 

 tubes and the interspaces appear to have changed places entirely. 

 Thus the »pseudopores" lead into more or less regular tubular 

 canals, while the »oscula" comraunicate with the irregular wide 

 spaces, the latter representing the widened original Ascon-tubes, 

 the inside of which is lined by choanocytes. On the other hand 

 the regular tubular canals are lined on the outside by choanocy- 

 tes. There is a communication between the two systems by means 

 of small apertures , the »original pores". The author calls this 

 phenomenon »reversal of the canal system". 



