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Group Tubifera. 



Under the above name we may unite the three following families, in which 

 the descending cryptocyst forms or takes part in forming a shorter or longer, 

 more or less complete, more or less insymmetrical tube, the polypide tube, 

 the frontal wall of which from a deeper level ascends towards the aperture. 

 In all the members of this group a part of the cryptocyst descends more 

 or less deeply into the zocecium, generally in such a way as to join the basal 

 wall with a shorter or longer basal edge on each side, but in a few cases these 

 outgrowths from the cryptocyst only reach the basal wall (Steganoporella Haddoni, 

 St. Buski) or the outgrowth on the one side only reaches the lateral wall (some 

 Thalamoporella-STpecies). While the frontal wall and the lateral walls of the 

 polypide tube are always formed by the cryptocyst, the basal wall is in most 

 cases formed by the basal wall of the zocecium, and in such cases the outgrowths 

 join this wall with a curved or angular edge on each side, the distally ascending 

 parts of which indicate the form and direction of the tube (PI. V, fig. 5 b, PI. VI, 

 fig. 5 d, PI. Via, figs, lb, 3e, 4 b etc.). More rarely the polypide tube has a 

 basal wall of its own, the two outgrowths from the cryptocyst bending round 

 and uniting within the basal wall of the zocecium, such forming a basal wall 

 for the polypide tube. In that case the two outgrowths join the basal wall of the 

 zocecium in a continuous, curved or angular line and distally to this is seen the 

 tube shining through the wall (PI. VI, figs. 3d, 7 i, PI. VI c, fig. 1 f). 



While in the Thalamoporellidae and in a few Steganoporella-species (PI. V, 

 fig. 3 a) the frontal wall of the polypide tube is distally on each side in con- 

 nection with the lateral parts of the cryptocyst, this is not the case in the other 

 members of the group, in which this frontal wall (the ^median process* Harmer 

 in the Steganoporellidae) is quite free. Thence follows, that in the Thalamo- 

 porellidae the »opesiulse« are completely separated from the aperture while in 

 the other Tubifera they are fused together with it, but this fusion can take place 

 in different degrees, and while in most species of the genus Steganoporella and in 

 the genus Aspidostoma the two opesiulse are seen as two rounded sinuations from 

 the aperture, they are completely melted together with it in St. lateralis and in 

 the genera Siphonoporella, Labiopora and Crateropora. 



In all such forms, in which the basal wall of the polypide tube is formed by 

 the basal wall of the zocecium, the opesiulae or the corresponding parts of the 

 aperture leads into two cavities (the > lateral recesses* Harmer), more or less 

 completely separated from the polypide tube and from the remaining zooecial 



