30 



THE CRUSTACEA 



laid the foundations of classification. The order Branchiopoda, as 



first defined by Lati^eille in 

 1817, included Ostracoda, Cope- 

 poda, and Limulus ; and Milne- 

 Edwards, in 1840, Avhile exclud- 

 ing these, retains the later added 

 Nehalia. Later attempts to 

 extend the limits of the group 

 to readmit the Ostracoda and 

 Branchiura have not met with 

 support, while Claus's demon- 

 stration of the Malacostracan 

 affinities of Nehalia and its 

 allies is now generally accepted. 

 Among the authors who, in the 

 first half of the nineteenth 

 century, contributed to a know- 

 ledge of the group, Jurine, 

 Fischer, and Baird may be 

 mentioned. Zaddach's mono- 

 graph on u4])us is still the chief 

 source of information on many 

 points of anatomy. Leydig's 

 work on the Cladocera is especi- 

 ally important as regards internal 

 anatomy and histolog}' ; and 

 Weismann's series of papers 

 deal, among many other points, 

 with the remarkable phenomena 

 of their reproduction, which had 

 attracted attention from the 

 time of Schiiffer. As is the case 

 with most other groups of Crus- 

 tacea, modern conceptions of 

 the morphology of the Branchio- 

 poda are largely indebted to 

 the works of Claus. Lankester's 

 paper on the appendages and 

 nervous system of Apns greatly 

 influenced opinion in favour of 

 the primitive position of the 

 Branchiopoda. Among the more 

 purely descriptive and faunistic 

 works the numerous papers of 

 G. 0. Sars hold an important place, and mention may also be 

 made of the fine monograph on the Cladocera of Sweden, published 



Fig. 15. 



Brawihincda paludosa, one of the Anostraca. 

 X 4. (After Sars.) A, female ; B, male, a', 

 anteimules ; a", antennae, enlarged in the male 

 to form clasping organs ; j), paired penes of 

 the male ; «<, ventral prolongation of the genital 

 segment in tlie female, containing the " uterus " 

 filled with eggs. On the front of the head, 

 between the antennules, is the unpaired eye, 

 and,.iust behind it, tin- stalked eoinijciiind pyc 

 Dorsal to the ]>i'ar-sliaiipd niaiidilili' is sn-n the 

 groove which a]i|ii'ars tn divide thn li.-ad-ri'gion 

 into two .s.-jinrnts. l-'ulhnving this, the trunk 

 sliMws rl,.\-rii liiiili-lH-ai iiig and cij^lit limbless 

 s.piiiitrs (licsidfs the telson), the first and second 

 of the latter partly coalesced. 



