A HISTORY OF WARWICKSHIRE 



Claus maintains that at least the little bleak and the minnow are as ready 

 to feed on the Argulus as the Argulus is to feed on them. Claus is will- 

 ing to retain the term Branchiura for this group, although objecting that 

 the tail is not in fact more branchial than some other parts of the body. 

 It is, indeed, he says, the seat of an extraordinarily rich and lively blood 

 circulation, and by its muscular arrangement is adapted for rhythmical 

 contractions and expansions, so that its function is that of an auxiliary 

 heart. 1 



In contrast with the foregoing very limited set of forms, the Clado- 

 cera, which constitute the remaining section of the Branchiopoda, are 

 a group of remarkable extent and importance in the fresh waters of the 

 world. Though in almost all species the individuals are small, and in 

 many descend to microscopic minuteness, they make amends for this by 

 their prodigious fertility. Like the aphides that infest our roses and 

 other plants, these entomostracans multiply by parthenogenesis. Milton 

 represents Adam as lamenting that the Creator did not ' fill the world at 

 once with men, as angels, without feminine.' Parthenogenesis is a device 

 for filling it ' without masculine,' and setting up a republic of amazons. 

 Nevertheless there come periods when it seems to be borne in upon the 

 minds of these self-sufficient females that nature is not completely satis- 

 fied with their procedure. They then form what are known as the 

 ' resting eggs,' which require to be fertilized by the male before they 

 are detached from the mother. They are then capable of ' resting ' for 

 long periods in mud, which may become thoroughly dry. When at a 

 suitable season water comes again to the soil the buried entomostracans 

 hatch out and a new cycle begins. 



In 1895 Mr. T. V. Hodgson, now engaged as naturalist on board 

 the antarctic exploring vessel, the Discovery, published a 'Synopsis of the 

 British Cladocera.' To this he appended a list containing all those species 

 which had up to that time been recorded from the neighbourhood of 

 Birmingham, 'a region which may be defined as being within a fifteen 

 mile radius.' 2 Mr. Hodgson has since informed me that as a matter of 

 fact all the species mentioned in the list have occurred in Warwickshire. 

 The question was raised, because localities are not in every case specified, 

 and a fifteen mile radius round Birmingham includes a district obviously 

 not conterminous with the county. The catalogue comprises twenty- 

 nine species and two varieties. Although these are far less than half the 

 number of British Cladocera now known, they involve almost all the 

 chief outlines of the existing classification. 



In the same year (1895) D r - Jules Richard began his excellent 

 Revision des Cladoceres with the following definition of this group : 

 ' Entomostraca free, minute. Head distinct. Rest of the body as a rule 

 laterally compressed and covered by a bivalved test. Second antennas 



1 Zeitichrift fur wissenschaftfiche Zoo&gie, xxv. 269 (1875). 



8 Journal of the Birmingham Natural History and Philosophical Society, vol. i. No. 19, pp. 101-112 

 (February, 1895). It will be understood that subsequent quotations, where not otherwise indicated, 

 refer to this paper. 



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