1894. NOTES AND COMMENTS. 247 



we see that their shells may safely be taken as zonal indices, since 

 they mark truly contemporary divisions of the earth's crust whereso- 

 ever chey occur ; while, since their distribution must have taken 

 place after the death of the animals, they afford us no evidence as to 

 the environing conditions that may or may not have governed their 

 evolution. 



MoLLUscAN Mimics. 



Our ignorance as to the mode of life of extinct mollusca often 

 lands us in great difficulties, and problems continually occur of which 

 the solution can never be more than guessed at, although, could we 

 have but a glimpse of the once living animals, our questions might 

 receive an obvious and immediate answer. The curious resemblances 

 between species of totally different genera, may be explained in more 

 than one way, perhaps by action of similar environment, perhaps in 

 obedience to dimly-perceived laws of growth ; but it is not often that 

 we apply to them the explanation afforded by the biological pheno- 

 menon known as " Mimicry," not at least when we are dealing with 

 fossils. A paper recently read by Mr. A. H. Cooke before the 

 Cambridge Philosophical Society seems to show that we might 

 occasionally do worse than venture this answer to the riddle. He 

 reminded us that the shells of Strombus mauritiamis and 5. luhuamis 

 differed from those of all other Stvombi in their close resemblance to 

 the shell of Conns, a genus with which they were known to live. He 

 pointed out that Strombus was a vegetable-eater, with small weak 

 teeth, while Conns was a flesh-eater, with large barbed teeth, provided 

 with a poison bag and duct. Conns, then, would naturally be avoided 

 by predatory fish, and any resemblance to so dangerous a genus 

 would be of great advantage to Strombus. In the case of extinct 

 mollusca, a similar explanation might occasionally be possible, but, 

 of course, only when the species in question occur in the same 

 locality and bed. 



Chaos in Science Teaching in London. 



Some time ago (Natural Science, vol. iii., p. 297), in referring 

 a second time to the clever anonymous pamphlet on the Organisation 

 of Science, we urged that the existence of competitive journals and rival 

 societies secured freedom and prevented novel views being suppressed, 

 merely on account of their unorthodoxy. To a certain extent the 

 competition and rivalry among teaching bodies in London secures 

 flexibility and range in science teaching, and the present chaos of 

 institutions, which has come about by natural growth, has its good 

 side. On the other hand, much money and time is wasted by 

 unnecessary multiplication of teaching plant ; there is no coordina- 

 tion by which various institutions can as a right utilise each other's 

 advantages. The great libraries, museums, and teaching institutions, 



