CALMA GLAUCOIDES 443 



closely equitant on the rod. In sections stained with iron 

 haematoxylin and acid fnchsin this rod, which is the homologue 

 of the basal membrane of other radula, takes the acid dye, 

 while the teeth are a deep black. Even in potash preparations 

 the faint lines of demarcation of the individual teeth can be 

 made out under an oil immersion lens (see fig. 4). To the stout- 

 ness of the basal rod is due the fact that the radula is always 

 obtained complete and undistorted in preparations, as well as 

 its efficiency as a cutter of membranes. The most interesting 

 feature of the Calma radula, however, is the preservation at 

 its anterior end of the small first-formed teeth to the number 

 of four or more. These minute persistent teeth (fig. 4, 1-5) 

 are spaced out on their thin basal membrane and closely 

 resemble those of the uniseriate radula of Favorinus, being 

 without lateral denticulations. The basal membrane is con- 

 tinuous in front with the thick rod of the later radula. Between 

 this early normal Aeolidian radula and that of the adult is 

 a gap in which the dentigerous strip is already thickening, but 

 the teeth themselves are imperfect. Numbers 5 and 6 of the 

 figure look like imperfect Aeolidian teeth, while the remainder 

 of the gap contains irregular serrulations suggesting the 

 incipient adult structure. As this sequence is remarkably 

 constant, it is evident that here in the radula of Calma we have 

 a concise record of the change that occurs in the feeding 

 methods of the animal, for it is unimaginable that the minute 

 adult at the beginning of its career is capable of feeding on the 

 eggs of fishes. It is still more interesting as the preserved record 

 of the evolution of the Calma type from a more generalized 

 carnivorous Aeolid. 



The post-bulbar salivary glands (Text-fig. 1, s.g.) 

 consist of a pair of simple tubes, the walls of the distal part of 

 which contain very large granular cells. These bulge out 

 singly or in groups of two or three, and their cell-contents stain 

 deeply with the basic dyes. The salivary ducts pass through 

 the nerve-ring to open into the buccal cavity at the posterior 

 ventral edge of the lateral pads. 



The oesophagus is short and narrow, but its walls are 



