A STUDY IN MORPHOLOGY. 
Ill 
at successive moults do not admit of exact comparison with each other; the outcome, 
after a few moults, is almost exactly the same, as will be seen by a comparison of 
fig, 60 with fig. 90. 
The number and character of the somites and appendages is now the same, and 
while the two forms differ greatly in outline and proportion, the young Acetes is 
essentially like the young Lucifer, except in the length of the flagellum of the second 
antenna, the presence of chelae on the thoracic limbs, the presence of gills, and the 
absence of a “ neck. ” The outcome of the process of development is alike, but the 
paths followed diverge from each other to converge again at this stage. 
Comparison of Lucifer and Sergestes. 
The metamorphosis of Sergestes is more like that of Lucifer than is the case with any 
other known Crustacean except Acetes, but our knowledge of the development of 
Sergestes is incomplete, and we have no assurance that the various stages which have 
been described belong to the same species. 
In 1870, Dohrn described a remarkable larva (“ Untersuchungen liber Bau und 
Entwickelung der Decapoden, No. 10, Beitrage zur Kenntniss der Malacostraken und 
ihrer Larven, Part 4, Beschreibung einer neuen Decapoden-Larve,” Zeit. f. Wiss. 
Zool., xx., p. 607) which he collected at the surface at Messina, and which he was 
unable to refer to any adult form. He proposed for this larva the provisional name 
Elaphocaris. Elaphocans is a Zo'ea which so far as its appendages are concerned 
does not differ much from the last Zo'ea of Lucifer, but its abdomen is very spiny, 
and the spines on the carapace are drawn out so that each one of them is nearly half 
as long as the body, and they are fringed with rows of long secondary spines which 
are hooked at their tips, and so arranged as to give to the body a very grotesque 
appearance, and the larva does not, at first sight, show any similarity to the simple 
Erichthina larva of Lucifer. 
Claus had several years before described f Ueber einige Schizopoden und niedere 
Malacostraken Messinas,” Zeit. f. Wiss. Zool., xiii., 1863) a larval Crustacean with 
swimmerets, biramous thoracic limbs, and a very spiny body, which he calls an 
Acanthosoma. This same larva, or a very closely related form, had been figured and 
described nearly twenty-five years before by Dana ( c Crustacea/ p. 664, plate 44, 
fig. 5) as Sceletina armata. 
In the same paper Claus gives a figure of a young Crustacean, which had previously 
been described by Leuckart under the name of Mastigopus, and shows that it is in 
all probability a young Sergestes. 
In his ‘ Untersuchungen zur Erforschung/ &c., he describes an Elaphocaris at a 
much younger stage than Dohrn’s figure, and shows that this larva, Dohrn’s 
Elaphocaris, his own Acanthosoma, and .Leuckart’s Mastigopus are successive stages 
in the development of Sergestes. 
