472 TRANSACTIONS OF SECTION D. 



I suggest that the real explanatioa of male secondary characters is that 

 they are characters of abandoned function or their physiological equivalents — 

 suppressed in the young in favour of more essential growth (of organs still 

 fully functional), and in the adult female because, with her, nutritive surplus 

 is more directly diverted to the purposes of reproduction. Hence such 

 characters usually only find opportunity for full expression in adult males. 



Where an organ is in process of retrogression through loss of function, an 

 intermediate stage of extravagant growth under favourable nutritive conditions 

 may occur before the wholly rudimentary stage is reached. 



Secondai-y sex exaggerations may significantly parallel enlargements due to 

 accidental loss of function. The tusk of the male babirussa may be com 

 pared with instances of occasional circular overgrowth in the tusk of the 

 hippopotamus, or with the elongation of a rodent's incisor when the opposing 

 tooth is lost. 



The dependence (usual amongst vertebrates) of the development of the 

 secondary character on the active presence of the male gonad may, perhaps, be 

 explained by reference to the phenomena of periodicity. 



Through inherited correlation, the activity of the gonads influences the 

 nutritive bias in the direction of reproduction, the related physiological ' ebb 

 and flow ' being on an enlarged or more cataclysmic scale, as it were, and so 

 affording latent characters opportunity for expression (in males). This sug- 

 gestion is rather supported by the fact of the renewal of the secondary feature 

 at the breeding season in various types. 



5. Studies on the Biology of the Appendix Vermiformis in Monotremes 

 and Marsupials. By William 0. Mackenzie, M.D. 



The following animals were considered : Monotremata : Ornithorhynchus and 

 Echidna ; Marsupialia : Phascolarctos, Phascolomys, Dasyurus, Macropodidae, 

 and Trichosurus. 



Attention was drawn to the fact that one Monotreme (Ornithorhynchus) has a 

 caecum and the other (Echidna) a true vermiform appendix comparable, macro- 

 scopically and histologically, to that of man, ape, and wombat — the three 

 mammals regarded as having a true vermiform appendix. Various grades of 

 degeneration in the appendix of Echidna were demonstrated. Amongst the 

 iVIacropodidae, the wallaby and the kangaroo exhibited a well-marked difference 

 in the csecal region. In Phascolomys the appendix was shown to have reached 

 a much more advanced degree of degeneration than that of man — even to 

 complete disappearance. The mode of disappearance is by incorporation in the 

 wall of the ileum, and of this the varioiis gradations were shown. This animal, 

 then, presents suggestive evidence of the mode of the further degeneration of 

 man's appendix. No cases of inflammation of the caecal region have been met 

 with amongst the Phascolomyidre. 



6. Regeneration of the Tail in the Common Lizard (L. vivipara) after 

 Autotomy. By Charles Powell White. 



The lizards which form the basis of these observations were found under 

 natural conditions in North Wales. 



Autotomy takes place through the middle of a vertebra. There is no special 

 autotomy-site as in the legs of crabs, but apparently any vertebra may be 

 involved. Regeneration may continue tmtil the regenerated tail is fully as long 

 as the original one. 



In such a fully regenerated tail are found : 



1. The skin and subcutaneous tissue. 2. The muscles situated beneath the 

 skin to which they are attached. They consist of sixteen longitudinal bundles 

 and are also segmented transversely in zig-zag rings, each segment apparently 

 corresponding to a ring of scales in the skin. 3. Beneath the muscles is a layer 

 of fatty connective tissue in which rim nerves and blood-vessels. All the 

 nerves are derived from the last three pairs of nerve roots in the stump of the 



