A STUDY IN MORPHOLOGY. 63 



and show the embryos in dorsal view, as seen under a very low magnifying power, 

 but they are so much like FRITZ MULLER'S figures, that we must acknowledge that 

 the credit of the first discovery of a Malacostracan Nauplius belongs to DANA, and 

 that up to the present time this is the only case in which a Nauplius has been traced 

 to an egg which could be definitely identified as that of a specific adult Mala- 

 costracan, although his account is so imperfect that in itself it is certainly not 

 sufiicient to prove the existence of the Nauplius stage at all. 



In 1861 FRITZ MULLER found, at Desterro, in Brazil, a single specimen of a Nanp- 

 lius ("Die Verwandlung der Garneelen." Erster Beitrag von FRITZ MULLER, in 

 Desterro, Arch. f. Naturgeschichte, 1863, p. 9), which he traced, through other speci- 

 mens winch were also collected in the ocean, to a form which he believed to change 

 into the youngest Zoea of a species of Penceus. The series of stages is so satisfactory 

 that there is no reason for doubting the accuracy of his conclusion, but the chances 

 for error, in the attempt to trace Crustacean development from isolated specimens, are 

 so very great that the statement has not received unqualified acceptance. 



The only other recorded observation of a Malacostracan Nauplius is not among the 

 Decapods, but in the more embryonic Schizopods. These observations, which were 

 made by METSCHNICKOFF, would tend to corroborate those by MULLER, but they are 

 unfortunately open to the same criticism. He did not actually rear the larvae and 

 trace them to a specific adult, and although there would in ordinary cases be no doubt 

 of the correctness of his conclusion, a careful analysis of his papers will show that 

 there certainly is a possibility of error. 



In the spring of 1868 he collected from the surface of the ocean at Messina a few 

 early stages in the development of a Crustacean, which he believed to be Euphausia 

 mulleri (GLAUS), and showed (" Ueber ein Larvenstadium von Euphausia " von 

 EL. METSCHNICKOFF in Petersburg, Zeit. f. Wiss. Zool., xxix., 1869, p. 479, taf. xxxvi.) 

 that it passes through a well-marked Nauplius stage, of which he gives three figures. 



The following year, at Villafranca, he collected a good supply of young Iarva3 and 

 floating eggs in advanced stages of development, and was thus enabled to supplement 

 his first paper by a second (" Ueber die Naupliuszustande von JHuphausia," von ELIAS 

 METSCHNICKOFF, Zeit, f. Wiss. Zool.7 xxi., 1870, p. 380, taf. xxxiv.) in which he gives a 

 minute account of the Nauplius from the time it leaves the egg until it changes into a 

 form somewhat similar to the youngest stage of Euphausia, which had been previously 

 described by GLAUS (" Ueber einige Schizopoden und niedere Malacostraken Messinas," 

 von Prof. Dr. C. CLAUS, Zeit. f. Wiss. Zool., xiii., 1863, p. 422). CLAUS had supposed 

 this to be the stage in which the larva leaves the egg, and he says (p. 450), " Diese 

 Larve bin ich geneigt fur die jiingste aller freieren Entwickelungsformen der Euphausia 

 anzusehen." He subsequently learned, however (" Untersuchungen zur Erforschung 

 der Genealogischen Grundlage des Crustacean-Systems," p. 9), that he had been in error, 

 since he afterwards found, in an Atlantic and also in a Mediterranean species, an earlier 

 Protozoea stage, which changed into the Zoca described in his first paper. It therefore 



