22 TAOr: sKor..si;Ki;c; 



coxalc. Till' exopoditc anil tlu' ('iiilopodiU' ol thi' hirainnus limb art' in most cases divided 

 into a larger or siualliT iiuiiiber of joints, which are usually distinct. 



The third type, the rod-shajied limb, is usually well jointed and consists of a single row of joints. 



The chief function of the foliaceous limb seems to be that of locomotion, swimming, and 

 its secondary functions are those of respiration, carrying the food to the mouth, breaking up 

 the food, etc. In the biramous limb these functions are differentiated and localized; the exo- 

 podite and eudopodite are specially adapted for locomotion and the epipodial appendages 

 espiTiallv are used in respiration; the endites on some of the limbs situated nearest the mouth 

 are differentiated for the function of taking up food. The rod-shaped limbs are especially 

 Incnmotory organs, functioning chiefly as organs for crawling and climbing. 

 Wlnchof ihi:sr ti//>cs Which of thcsc three types is to be considered as the most primitive? This seems an 



i!-tie»iosipnnntn-e. (,^^.^,^,^[^^J^^g\y difficult question to answer. 



It is rather common nowadays to consider, with Rav LaNKESTER, the first type, the 

 li)l)ed foliaceous Unib as most primitive (e. g. \\. (tIESBRECHT in his comjsrehensive work on 

 the Crustacea, 1913). It is this type that we find in the P h y 1 1 o p o d s. the group that is 

 now generally and presumably correctly consitlered as the most primitive of all the recent 

 Crustacea known at present. 



Another view is maintained b\- <-'. Clal s. This eminent investigator of Crustacea writes 

 as follows in his important work of 1876, p. 17: ,.Demnach wiirden wir zu dem gewiB nicht xm- 

 berechtigten Schlusse gefiihrt, daB die Extremitaten der Stammkrebse, iiber deren Bau uus 

 leider die iiltesten palaontologischen Crustaceenreste zur Zeit keine Auskunft geben. keines- 

 wegs echte blattformige PhvUopoclenfiiBe waren, .sondern den UliedmaBen von N a u j) 1 i u s 

 iihnlich, eine Annaherung an die SpaltfilBe zeigten. welche nun um so leichter in einseitiger 

 Streckung der Aeste, den sich nach einer anderen Richtung mehr flachenhaft gestalteten Phyllo- 

 podenfiifien gegeniiber, ihre Eigenthumlichkeiten ausbilden konnten.'' According to this author 

 (p. 1(5) the epipodial appendages are later acquisitions. 



E. KORSCHELT and K. Heider seek the original ty[)e of the limbs of the Crustacea in 

 the bifurcated parapodium of the A n n e 1 i tl s. In their textbook of 189(», p. 389 these authors 

 write as follows: ,,Man ist versucht, die typische zweiastige Form des Crustaceenbeines direct 

 von del- ahnlichen gegabelten Grestalt der Annelidenparapodien herzuleiten. Hierfur spricht 

 ilie eben etwahnte Thatsache, ilaB die Sonderung von Exoi)odit und Endopodit sich an den 

 Beinanlagen von Branchifu^ ungemein friihzeitig geltend macht." The endites are according 

 to these authors new acquisitions; the epipodial appendages, on the other hand, are fU'imitive 

 organs, which ,,man wohl mit einiger Wahrscheinlichkeit auf Dorsalcirreu der .Vnneliden 

 beziehen diirfen'". ,,Gegen letztere Auffassung spiirht allerdings das verspiitete Auftreten 

 die.ser Bildungen in der Ontogenie der Crust a c e e n. Doch darf man nicht vergessen, daB 

 eine Steigerung des respiratorisihen iiediirlhi.sses erst bei einer gewissen KorpergroBe si^h 

 geltend zu luarhen pllegt und es soniit erkliiilirh scheinf. weiin kleine Krebslarven (ebenso 

 wie ausgebildete b'oinieri von geriuger Korperentwicklung) der Kienienanhange entbehren." 



J. Tllll':i,l': also starts nul from the idea that the parapodium of the Annelids 

 is the original type of the Crustacean post-oral limbs. This author writes, 1905. [). 467: 



