252 PKOCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



differences in the radula and jaw, and in the shell, which the mantle 

 lobes cover to a greater extent ; these divergences are only such as 

 might be expected when the great extent of country intervening is 

 considered. Our member, Mr, Webb, has lately re-examined this 

 genus and confirms my original views. I have also, when lately 

 working out the retractor muscle system of Girasia, examined that of 

 this southern genus also. The agreement is very great ; no difference 

 either is to be found in the form of the spermatophore.^ 



T would here make a few remarks on these curious and beautifully 

 formed structures ; they have not received the attention they demand 

 in classification, except from a few biologists. In looking at the 

 modification and intricate details they present, we are brought to 

 consider the vast interval of time it must have taken to effect changes 

 in any group of animals, particularly in the mollusca ; the thousands 

 and thousands of years represented by the Tertiary Period does not 

 seem enough for this evolution. How vast it becomes when we try 

 to reconstruct the form of the spermatophore in the Zonitidae before 

 they began to branch off one from the other ! "We see that in the case 

 of such an excretory instrument as a spermatophore any change in the 

 proportions or details of its different parts, is the result of modifica- 

 tions that have taken place in the interior of another organ within 

 which it is moulded, and, again, a proportionate change in that of 

 another organ, the spermatheca, within which it comes to finally rest. 

 "When we are trying to extend our knowledge of geographical 

 distribution we cannot be too particular, or afford to neglect any 

 morphological details that are presented to us. "While a great deal of 

 small minor variation has gone on, in a broad sense quite recently, in 

 the form of the shell, in its sculpture, etc., there has not been, on the 

 other hand, so great an amount of what constitutes true generic 

 change. In this family of the Zonitidse, as represented in India, the 

 spermatophore illustrates this. Only four well-marked and specialized 

 types have been noticed by me, up to the present, occurring in the 

 genera: {V) Macrochlamys; (2) Ariophanta and JVilffi'ria; (3) Girasia and 

 Austenia ; (4) Euplecta ; this last being the most differentiated. These 

 structures will accentuate the value of certain main groups when the 

 time comes to decide upon them. There is, however, an enormous 

 amount of material to be examined, and until this is done we should 

 hold back from the creation of these divisions and subdivisions, at 

 which there is a great tendency to play, and occasionally we see no 

 attempt made to describe the particular characters that mark off one 

 division from another. 



It truly comes to this, the examination of the spermatophore of 

 every species among the Zonitidfe would be far more satisfactory 

 than that of the muscular tube that surrounds it, for in the 

 spermatophore we have reached the end of a stage of development, 

 the resultant of original birth and existence about to begin again, 



^ The restoi-ation of this from broken portions, figured by Mr. Webb (ante, pi. ix, 

 fig. 6), is not by any means true to nature. 



