NATURAIv HISTORY OK AMERICAN LOBSTER. 



223 



great chelipeds and the first pair of swimmerets. The complex and varied relations 

 of the successive somites and appendages of the lobster in the larval and adult state are 

 outlined in table 4. 



In their type form (fig. 2 and pi. xxxvi, fig. 5) the appendages consist of an inner 

 and outer branch borne on a basal stem, known respectively as endopodite, exopodite, 

 and protopodite. The protopodite is composed of two segments, a proximal coxa, or 

 coxopodite, and distal basis or basipodite. The coxa of each limb from the maxillse to 

 the fourth pair of pereiopods (somites v-xiii) bears a hairy respiratory plate or epipodite, 

 from which rises a gill or podobranchia on all but the first two of these somites. The 

 primitive type of crustacean Hmb was probably biramous, since in the course of develop- 

 ment we frequently find the uniramous condition produced by loss of the more transi- 

 tory exopodite, and further, since the f oliaceous form of appendage of the lower branchio- 

 pod Crustacea is secondarily assumed by certain of the mouth parts of the lobster and 

 other decapods. The undivided form of limb is permanently preserved in metameres i 

 and x-xv, in the last of which the appendage is modified in the two sexes to perform 

 distinct functions. The origin of the two-branched antennules will be considered 

 presently. The exopodite is frequently abortive, or multiarticulate and elastic, as in 

 the swimmeret, a condition which the endopodite has also preeminently assumed in 

 the long whips of the antennae. 



WITH THEIR Chief Functions and Modifications in Larva and Adult. 



Relation, erf appendage to type form. 



Relation of adult to embryonic and larval ap- 

 pendage. 



Apertures of body. 



Doubtful; stalk in two segments 



Doubtful. Basal segment lodges statocyst sac. 



Exopodite wanting; exopodite reduced to scale, 

 and endopodite irregularly segmented. 



Biramous; two distal segments of palp supposed 

 to represent the endopodite. 



Foliaceous; exopodite wanting; endopodite of 

 two modified segments. 



Biramous and foliaceous; respiratory fan formed 

 by fusion of exopodite and epipodite. 



Biramous and foliaceous, and like maxillae, with 

 protopodite modified for testing and passing 

 the food. Endopodite 2-jointed. 



In type form; endopodite 5-joiuted, and epipo- 

 dite with rudimentary gill. 



In* type form, modified for mastication, and 

 cleaning; second and third podomeres fused, 

 and exopodite reduced. Epipodite with func- 

 tional podobranchia in ix-xra. 



Uniramous through loss of exopodite in fourth 

 stage. Second and third podomeres modified 

 for autotomy, and fused "breaking joint" be- 

 tween them. 



Uniramous through loss of exopodite in fourth 

 stage. 



The same 



The same 



The same, without epipodite and podobranchia. 



Transitory ocellus in first larva; compound eye 

 relatively large, and stalks short. 



Bifid, and later imiramous in embryo; finally bi- 

 ramous in first larva; inner fiagellum a secondary 

 outgrowth from primary stalk. Prostomial. 



Bifid, and later completely biramous in embryo; 

 poststomial in origin, but later advance in front 

 of mouth. 



Body and palp at comparatively late embryonic 

 stage. 



Early larval condition similar to adult, but endo- 

 podite imsegmented. 

 First larval condition similar to adult 



The same, but epipodite without fold for *' bailer " , 



First larval state similar to adult. , 



In first larva with long swimming exopodite, lost 

 at fourth stage, and third joint free; no cleaning 

 brushes, and no teeth on ischium. 



Biramous to fourth stage. Big claws nonprehen- 

 sile in first larva; of toothed type in fourth, and 

 symmetrical up to sixth or seventh stage. Tor- 

 sion of limb completed at fourth stage, after 

 which big claws are horizontal, and dactyls face, 

 opening toward mid-line of body. 



Swimming exopodite shed at fourth stage 



The same 



The same 



The same; torsion of terminal segments away from 



mid-line of body completed at fourth stage, when 



limb is directed backward. 



Pore of statocyst on up- 

 per surface of basal 

 segment. 



Papilla for opening of 

 renal organ on coxa. 



Mouth , screened by 

 1 a b r u m, between 

 mandibles. 



Oviduct opens on coxa. 

 Seminal receptacle. 

 Vas deferens opens on 

 coxa. 



