W. LEUCKARTI. — GEN. CHABACTEES. 283 



On the other hand, the gastral surface of the wall (see PI. 

 XIII, fig. 5) shows the inner system of weaker and more widely 

 set parenchymal strands which are directed in the main trans- 

 versely or obliquely. Thus it will be noticed that the general 

 arrangement of the parenchymal strands is the same as I have 

 described for Regadrella. 



The small irregular meshes on the gastral surface, formed 

 by the intersecting of parenchymal strands, are each occupied by 

 a shallow or pit-like depression, the excurrent canal. 



What now give the most characteristic feature to the species 

 are the branches and wart-like tuberosities, which latter occur on 

 both the stem and the branches but more numerously on the 

 branches. 



Let it at once be stated that the branches arise by growth 

 from the wart-like tubercles, and that the production of both is 

 evidently dependent upon the commensal Hydroid colony tenant- 

 ing the sponge-wall, as has been maintained by F. E, Schulze 

 also in the case of certain tulnilar structures in W. Jlcmmingl. 

 The branches in W. leuckarU are in a sense comparable to, 

 although genetically different from, the ledges of J^ujjlectella, the 

 stem being the most essential part of the body. 



The tubercles are sometimes low and not at all pronounced ; 

 sometimes distinctly wart-like or even tubular. Seen under a 

 lens, they present a hispid exterior on account of the dermal 

 hilt-rays. (PI. XIII, figs. 20, 21). Their general aj^pearance, 

 especially as they stud the branches, reminds one of the polyparies 

 of a Madreporarian skeleton, and that all the more, since each 

 tubercle has a small opening in its summit. The more pro- 

 minently developed tubercles have more than one opening besides 



