peesident's address. 279 



development of this contact fuiTow and its beginning, the impressed 

 zone, as an ' acquired characteristic,' it being one that originally had 

 no existence in the phylogeny of the race, but was developed later. 

 Whether the teachers of recent morphology will accept this definition 

 is another matter, for unlike palseontologists they expect more 

 immediate results. 



While so much has been done in unravelling the evolution of the 

 Tetrabranchiate Cephalopoda, more still awaits solution, especially 

 among the earlier forms, and the Dibranchia are practically untouched.^ 



Following in the footsteps of Hyatt, under whom he in part studied, 

 E.. T. Jackson began similar researches among the Pelecypoda, and 

 dealt with the Aviculidte (i.e. Pteriidte) and their allies [IfS). 



His work, unhappily, does not carry the same conviction with it as 

 Hyatt's. For this the subject is to blame. The prodissoconchs of 

 Pelecypods seem to afford fewer characteristic features than the proto- 

 conchs of Cephalopods, while the later stages exhibit no such marked 

 intrinsic features as do the septa of Ammonoids and Nautiloids. 

 Moreover, the author's genealogical table shows that his conclusions, 

 when dealing with genera having modern representatives, do not 

 coincide with the teachings of investigations founded on the animals 

 and their embryology. 



Another attempt to deal with the Pelecypoda from the evolutionary 

 point of view was unfortunately brought to naught, for the intervention 

 of death cut short the projected Avork of Felix Bernard (5), which gave 

 promise of ably carrying through the task of tracing out the ontogeny 

 and morphology of the Pelecypod shell so far as the Tertiary and 

 Recent forms were concerned. As was to be expected from his previous 

 investigations (2), the development of the hinge took a prominent 

 place in these researches. The work is a fragment, but wo are 

 fortunate in possessing even that from so able a pen. 



With the exception of these two writers, Jackson and Bernard, no 

 one seems to have taken up the study of the Pelecypods from the 

 detailed evolutionary point of view, and there is therefore a wide and 

 important field of research awaiting due investigation. 



What opportunities for evolutionary research the Gastropoda offer 

 has of late been shown by the series of valuable papers by A. W. 

 Grabau {26-9), that deserve the careful attention of all Malacologists.^ 

 His examples are chiefly drawn from families high up in the 

 phylogeny of the race {Fastis, Murex, Sycotypus, Fulgxir), and so do 

 not afforcl scope for any really wide generalizations; nevertheless, they 

 teach much, as the following resume of his conclusions will show. 



For purposes of study the Gastropod shell presents an advantage over 



1 In the foregoing observations on the Cephalopoda I have had the advantage of 

 Mr. G. C. Crick's kind assistance and advice, and I gladly take this opportunity 

 of returning to him my sincerest thanks. 



- The classical work by Neumayr {51a) on the evolution of the species of Vivipara 

 in the Neogene beds of Slavonia, with Hilgendorf's {30a-c) and Hyatt's {3Sa, h) 

 papers on the phylogeny of the forms of Planorbis multiformis from the Miocene 

 of Steinheim, being limited in their scope, need not detain us, valuable as 

 they are. 



