MUSEUM OF COMPAKATTVE ZOOLOGY. 255 



the body. Its further course was not determined. The two posterior vessels 

 correspond to the superior abdominal and sternal arteries of the adult. I was 

 unable to discover any vessels answering to the antennary and hepatic arteries 

 of the adult. 



After issuing from the ends of the arteries, the blood may be seen coursing 

 through the cavities of the body back to the heart. Two of these currents 

 are evident in the abdomen, one above, and the other below, the abdominal 

 artery. The venous blood in the cephalo-thorax streams back from the head 

 along the border of the carapace and upward to the heart. No traces of gills 

 exist at this stage. The blood is aerated in a great measure, probably, through 

 the thin walls of the carapace, currents of water being kept up, as in the gill- 

 bearing adult, by the constant motion of the scaphognathite of the second pair 

 of maxillae. 



The integument is nearly colorless and transparent, with a few blotches of 

 bright red pigment. The largest of the pigment-spots are, one on the lower 

 side just back of the mouth, two on the carapace at the points where the 

 lateral spines subsequently appear, and two on the telson (one on either side 

 of the anal opening). Beside these there are a few smaller specks of pigment 

 on the carapace and on the second, third, and fourth segments of the abdomen. 



It will be seen, from the foregoing description and from the figures, that we 

 have the same stage of the larva as that noticed by Fritz Muller on the coast 

 of Brazil in the case of Hippa emerita. Of this a brief notice and an unsatis- 

 factory figure are given in his work " Fitr Darwin." * Up to the time of 

 Smith's observations this was all there was known of the developmental his- 

 tory of Hippa. The notice is very brief : " The zoea of the Tatuira [Hippo, 

 emerita] (Fig. 25) also appears to differ but little from those of the true crabs, 

 which it likewise resembles in its mode of locomotion. The carapace possesses 

 only a short, broad frontal process ; the posterior margin of the tail is edged 

 with numerous short seta?." 



Professor Smith says : " Very nearly fully developed embryos, when re- 

 moved from the egg, were found to possess all the normal articulated appen- 

 dages of the fully formed zoese, but there was no appearance of lateral spines 

 upon the carapax, and the rostrum was broad and obtuse. In this stage the 

 embryo agrees almost perfectly with the figure of the zoea of Hippa emerita 

 from the coast of Brazil, given by Fritz Muller in his work entitled ' Fur Dar- 

 win.' The difference between the embryo in this stage and the second zoea- 

 stage [i. e. the stage presumed to be the second] (Plate XLV. Fig. 1), in which 

 the rostrum and lateral spines are enormously developed, suggests the pos- 

 sibility that Muller had observed only imperfectly developed young zoeae in 

 which the rostrum and lateral spines were not expanded. It seems scarcely 

 probable that such a difference could exist between the first stage of the 

 zoea, when the veiling membrane, in which, on first escaping from the egg, the 



* Fur Darwin. 1864. English Translation by W. S. Dallas, pp. 53, 54 ; Fig. 25. 



