3S0 



ARTHROrOPA 



(hl;. 40^) these all ilow together iii. a eummoii mass, connected with the 

 brain bv two loug ;esophaL;eal conrniissures. 



The dovelo|Mno',it of most decapods is interestiiiL; from the number of larval 

 forms. As a rule a .^ea liii,'. 370' is hatched from the ei;!;; this iias.;es next into 

 a Mysis stac'C vhg. 403) in which head, thorax, and abdomen are distinct, the 

 thorax bearing Idramous feet like those of schi/opods — a proof of the origin of 

 the simple feet from die hiramous t\-pe. In the crahs (^lirachyura) the Mysis 

 staije is replaced l>\- a Mei;alo}is ^Ul;. 404b in which the abdomen is well de- 

 veloped, but the feet ha\e lost their biramous character. In some prawns 



Fto. 401. 



Fig. 402. 



Fig. 401. — Rcpro.lucli\e origans of (A) female an,l v/'^l ni:\le crayllsh (frum 

 Huxle\0. ,)(.', oviilucl; ihi'. its opening; on iilh ap]iciiiU\L;i,'; (>-;■. ovary; /, tesU's; vii, 

 vas ileferens; i-a'. its oponiiiL; on pith ai'pcnilaLi;c. 



Fig. 40;. — Xorxous s\-slem of crah. (^\)r,iiiiis (from I '.ci^enbaurb iJ, anlrnual 

 nc^^■es•, c, ivsoi'hai;eal eomiuissurcs; i;/, fused ventral ehaia perforated for sternal 

 arlcr\'". t;.^", brain; t), L>ptie ner\"e. 



(Priini.':) the series is rendered more complete b}' the a[i]H'arance of a nau|)lius 

 and a mctanauplius wilh maii\' appendages, betore die .;iieal sl;ige. \n the 

 cravlish and manv land oralis the metamorphosis has been lost, but the lobster 

 leaves the egg in the M\sis stai^e. DilTerenees may occur e\en in the same 

 species; thus in tlie hatropean Palivnhviiics I'liriiiiis the enibrvo, in the sea, leaves 

 the egg as a .',oea; in fresh w;iter in the Mysis-sUtge. 



Sub Order 1. ,M.\Ci\UKA. .VlHlomen large; anlemi;e long; ventral iierx'e 

 chain elonijate; no mei^alops in development. C ARini'".\. Hod\' compressed; 

 no sutures on carapace; feet weak, external maxillipeds pedifoiaii; a larL;e scale 

 on second anieiinax rixnivi;, we;d-; exo]ii>ililes. l\i:rus/-' SiiViiiiid/'' Fai.- 

 .■EMoxaD t;, mandibles bil'id at tip. I\ila~i)i 'ii, Alf^hfus.'^' J [if'/yolxlf,''' /\;;/(/ii/((,v.* 

 CRANaioxm 1:, mandible simple. ('ra»ge/;,-'- .Siihi'icn.'''- .\S'V\COW]\.\. C:\v- 

 apaee crossed liv a, trans\erse groo\'e. .\sTAiaii i" have well-developed chela\ 

 Caiiibani.v''- includes the ci'a\iisli of the easlern slates; those of the Facilic coast 

 and Europe belong to Astiuns:''' Honuinis,'''- lobsters. Fai IM-Kin.i', (T^iricata), 

 no chclx, bodv with heavv armor; larvv leafdike (fig. 4oO. Palinjinis,^ s]iinv 

 lohster. P.\GURl'Dlv\, hermit crabs; abdomen reduced, soft-skinned, and 

 hidden in a snail shell which the animal carries about, which li;is resulted in a 

 spiral abdomen. Some hermits carry sea anemones or hvdroids on their shell, 



