442 



ZOOLOGY AT THE BRITISH ASSOCIATION. 



Prof. G. H. CARPENTER. 



The zoologists of the Association were admirably housed in 

 the Royal College of Surgeons, Professor Alex. Fraser acting 

 as local secretary, and making excellent arrangements. Dr. S. 

 P. Harmer, F.R.S., of Cambridge, was President of the Section. 



In his address. Dr. Harmer dealt particularly with the mor- 

 phology and variability of the Polyzoa, a group in which, as he 

 reminded the Section, an Irish zoologist, J. Vaughan Thomp- 

 son, was the pioneer student, and G, J. Allman, another Irish 

 naturalist, author of the ' classical monograph.' Dr. Harmer's 

 own researches on the Polyzoa are known to all zoologists. 

 In a lucid and comprehensive survey of the Polyzoan ' colony,' 

 he discussed the function of the curiously modified individuals 

 known as ' avicularia,' supporting the view that, ' like the 

 pedicellariae of Echinoderms, they are defensive organs,' and 

 that there services are valuable against ' encrusting organisms, 

 including other species of Polyzoa ; . . indeed, the enemies 

 against which a polyzoon has to provide are probably in a 

 special degree the members of its own class.' Attention was 

 called to the extreme variability of the avicularia among the 

 Polyzoa, and the difficulties raised by this variability. ':What 

 conclusions can we draw from the association in one and the 

 same colony of the vicarious type of avicularium with adven- 

 titious avicularia of the most speciahzed description ? How 

 can we explain the fact that each kind of avicularium occurs 

 in certain species, but not in all the species, of many distinct 

 and not specially related genera ? And lastly, what is the 

 significance of the fact that certain species of a genus which is 

 normally provided with avicularia may be totally destitute 

 of these organs ? ' It is not surprising that Dr. Harmer, 

 meditating on these problems in the Cambridge of the twentieth 

 century, suggests ' that some of our difficulties might be re- 

 moved by appealing to the results obtained by workers on 

 Mendelian inheritance . . . that the perplexing occur- 

 rence of vicarious avicularia in some of the colonies of certain 

 species may be interpreted as a reversion due to the combina- 

 tion of two or more allelomorphs that may not have occurred 

 together in the parental forms.' 



The meetings of Section D were, on the whole, of very 

 great interest. Perhaps the most striking feature was a joint 

 •discussion with Section K on the ' Determination of Sex,' 



Naturalist, 



