438 CEUSTACEA. 



The internal organization recalls that of the Phyllopoda. The 

 nervous system is distinguished by the great size of the cerebral 

 ganglion, and by the ventral chain composed of six closely approxi- 

 mated ganglia, In addition to two large compound lateral eyes, 

 there is present an unpaired tri-lobed median eye. The alimentary 

 canal consists of a short arched ascending oesophagus, a wide stomach 

 with two lateral ramified appendages, and a rectum which runs 

 directly backwards and opens to the exterior in the median indenta- 

 tion of the caudal fin above the two plates, which correspond to the 

 caudal fork. There are two lateral slit-like apertures in the heart, 

 and a long aorta. The entire surface of the cephalothorax functions 

 as a respiratory organ. There seems, however, always to be a 

 specially strong current of blood in the caudal fin, so that this part 

 of the body may be regarded as a sort of gill. 



Reproduction. The small, more agile male possesses peculiar copu- 

 latory appendages on the posterior swimming feet. The females do 

 not carry their eggs about in sacs in the typical Copepod manner, 

 but fasten them to surrounding objects. The vitelline membrane of 

 the deposited eggs acquires a vesicular consistence. The young are 

 hatched as larvae, and undergo a metamorphosis. 



Fam. Argulidae, Carp-lice. Arffiilus 0. Fr. Mull. The anterior pair of 

 maxillipeds modified into large suckers. There is a styliform spine apparatus. 

 A.foliaceus L. (Pou de poissons, Baldner) parasitic on Carps and Sticklebacks. 

 A. coregoni Thor., A r/iganti-iis Luc., Gyi'ojji'Jtis Hell. The rnaxillipeds end in a 

 claw ; styliform spine absent. G. Kollari Hell, parasitic on the branchiae of 

 Ilydrocyon, Brazil. G. Dora (? is Corn. 



Order 4. CIRRIPEDIA.* 



Fixed, and for the most part hermaphrodite Crustacea ivith indis- 

 tinctly segmented body enclosed by a reduplication of the skin, and a 

 calcareous valved shell. As a rule, there are six pairs of biramous 

 thoracic appendages. 



On account of the resemblance of their shell to that of the mussels, 

 the Cirripedia were held -to be Molluscs until Thompson and 

 Burmeister, by the discovery of their larva-, satisfactorily proved that 

 they belong to the Entomostraca. They are enclosed in a niussel- 



* Compare S. V. Thompson, " Zoological researches," Tom. I., 1829. H. 

 Burmeister, "Beitrage zur Naturgeschichte der liankenfiisslcr." 1832. Ch. 

 Darwin, "A monograph of the Sub-Class Cirripcdia," 2 vol., London, 1851-1854. 

 A Krohn, " Beobachtungcn iibcr die Entwickclmiir der Cirri pedien," Archiv 

 fur Natvrgcsch 1800. C. Claus, " Die Cypris-iilmlichc Larve der Cirripcdien, 

 etc," Marburg, 186'J. \\. Kossmauu, " Suctoria und Lepadiua," Wurzburg, 

 1873. 



