288 Henry Leslie Osborn, 



environment in which tlie animal lives. These wastes could however 

 be disposed of by confining them within the bodies of cells, 

 storing them where they would be under metabolic control. 

 It seems not unlikely that such is the meaning of the sub-cuti- 

 cular cells. 



At least two analogous cases exist, in widely separated groups, 

 where a similar problem is solved in this same way. One of these 

 is the case of the larval stage of the lepidopterous insects. These 

 find themselves, during pupation, enclosed within their case, so that 

 a discharge of the nitrogenous wastes would vitiate the environment 

 in which they are undergoing their transformation, and accordingly 

 the wastes is carried out and deposited in the scales, giving rise 

 to an important feature of the adult. In an analogous way the 

 larvae of certain prosobranchs, as for example Fasciolaria (Osborn, 

 1904) find themselves developing within impervious chitinous ^g^ 

 capsules. In correlation with this fact we find the development of 

 a very remarkable organ located directly under the velum. This 

 peculiar sub-velar organ is made up of modified ectodermal cells 

 which have become very much distended by an accumulation which 

 has crowded the cytoplasm and the nucleus into the outer end of 

 the cell where it constitutes a sort of cap between the secretion 

 within the cell and the cavity of the %gg case. (A view of the 

 structure of these cells is given in : American Naturalist, Vol 38, fig. 4 

 on p. 874.) 



We have now seen, in three cases of encystment or of condi- 

 tions closely analogous with it that storage activity manifests itself 

 in certain cells specialized for the purpose. If this storage in the 

 sub-cuticular layer of Loxogenes is correlated with encystment, then 

 we should expect to find that in related free forms the storage does 

 not take place. We have no recent papers dealing with the histo- 

 logical structure of any members of the Pleurogenetinae but fortuna- 

 tely a paper by Noack (1892) deals with the structure of Pleuro- 

 genes claviger in sufficient detail for our purpose. An examination 

 of his figs. 4 and 8 convinces one that a sub-cuticular layer is 

 present in Fleurgenes similar in character to that of Loxogenes. 

 Noack did not make a detailed study of the cells of this layer but 

 his figures show that they were in the same stage of activity as 

 that found in the specimens of Loxogenes from the frog's bladder. 

 It is difficult to believe that Noack could have overlooked them, 

 if such conspicuous cells as those of Figs, lo and 16 had been pre- 



