PACKARD.] EEPKODUCTIYE HABITS OF BEANCHIPODID^. 427 



The farther growth of the larva brings about an elongation and seg- 

 mentation of the body. The latter begins from the base of the body, 

 finally extending to its tip. 



A nearly perfect circnlar disc is seen on the anterior part of its dorsal 

 side ; this is the cephalic scute (carapace). 



"With the subsequent gradual development this scute retreats, confin- 

 ing itself in the adult to the occipital part of the head. In the base of 

 the second pair of antennaB 

 a rather large meandering 

 gland is seen whose outlet is 

 right below the first saber- 

 shaped flat bristle. This is 

 the so-called antennal gland, 

 whose presence has been as- 

 certained in most members of 

 this family of Crustaceans. 



* Below the middle of the pig_ 50_Streptoceplialus texamis. Left clasper of male 

 front of the larval head hangs larva with main brauch budding; tbe greater part of bris- 

 " J 1 1. 1 1X3-1 ties dropped, the remainder are shortened. 



down a short broad fleshy 



lobe, which in live specimens under the microscope is seen occasionally 

 to lift and lower again. This is the labrum, which we also find in the 

 adult in a somewhat reduced state. The median j)igmented eye on the 

 front of the larva is sessile, very simple, having but one pair of " corpora 

 vitrea" placed laterally. The Nauplius can distinguish light from dark, 

 but cannot discern the exact outlines of objects with it. 



The mandibular basal process of the third larval leg is transformed 

 into a mandible with a curry-comb-like dentation, and makes its ap- 

 IDcarance at the time when the fourth or fifth pair of branchipeds begin 

 to bud. 



A $ of 8treptocepJialus texanus had 22 flat acinaciform, long maxil- 

 lary teeth, and a very minute curved spine at the lower end. The first 

 of the teeth at the upper end has 14 spines, all the rest have 8 or 9 ; 

 the uppermost of them in each case being about twice as long and much 

 stouter. 



Transverse segmentation of the body always preceeds the lateral 

 budding of the branchipeds. 



The furca or terminal fork of the abdomen very early begins to bud 

 in the shape of two latero-terminal protuberances with two short min- 

 ute spines, and a little later another smaller lateral spine is formed. In 

 larvae of about 3.5™"^ in length, five such spines have made their ap- 

 pearance on each of the two protuberances. The number of spines, 

 with the middle one the longest, gradually after each moult, multiplies 

 until the typical furca of the adult is attained. Between the first pair 

 of branchipeds and the mandibulary palpus at an early age the two 

 pair of maxillse are formed, the first pair of which has in the adult 

 Streptocephalus the characteristic form as illustrated by Plate XXXIV, 

 fig. 7. In none of the numerous specimens examined by me could I ever 

 fiud a mandibulary palpus in the adult. 



When of about 3 or 4"^"^ in length, the second pair of antennse are re- 

 I)laced by another form, the old one gradually degenerating. First the 

 posterior, together with the two curved basal hooks, then the middle, 

 and finally also the terminal long bristles and inner branch drop oft' 

 from the inner side of the second antennse. In the interior of the second 

 antenna, near its base, an exuberant growth of cells takes place at this 

 time (Fig. 50). On the outer side, near the base, three i)rotuberances are 

 seen, from each of which groups of hyaline, rather stout and short spine- 

 like bristles arise. Their bases can be seen to originate from the deeper 



