Classification of the Crustacea. 457 



ment of many organs which ensue from these conditions. In 

 the case of the Cirripedes it is chiefly the developmental 

 stages that furnish the evidence necessary for the question of 

 origin. 



Among the Cirripedes the Lepadidse (forms like Pollicipes*) 

 are to be regarded as the most primitive. The first thing 

 which strikes us in the organization of this family, besides 

 the peduncle-shaped development of the cephalic end, is the 

 complete enclosure of the body by a mantle-shaped shell. 

 The mouth-parts are short, the mandibles devoid of palps, 

 the two pairs of maxillffi small. Of the two antennaj the 

 second has disappeared, while the first serves as an organ of 

 attachment. The six pairs of thoracic legs are provided with 

 long many-jointed rami thickly clothed with setai, and the 

 abdomen appears to be completely reduced. 



Above all, the mantle-shaped shell reminds us of the bivalve 

 shell of the Estheridge, and would afford justification for a 

 derivation from Archiphyllopods resembling Estheria. Yet 

 a closer consideration of the developmental stages shows that 

 such a derivation is incapable of accomplishment, since these 

 stages structurally conform to the conditions found in the 

 Copepods and in the Apodidte among the Euphyllopods. 



The extensive structural agreement between the develop- 

 mental stages of the Cirripedes and those of the Copepods 

 was demonstrated by Pagenstecher t and Claus J. The 

 Cirripede Nauplius closely resembles the Copepod Nauplius, 

 and in the so-called Ci/pris stage the shape of the thoracic 

 feet as swimming-appendages, as well as the segmentation of 

 the abdomen and the formation of the furca, repeat the con- 

 ditions which exist in the case of the Copepods. 



Since the idea tliat the Cirripedes are closely allied to the 

 Copepods appears to be thoroughly in accordance with facts, 

 it must also be possible to derive the Cirripedes, like the 

 Copepods, from Archiphyllopods which possessed the habilus 

 of Ajms. As a matter of fact, such points of agreement with 



* Cf. A. Weithofer, " Bemerkungeu liber eine fossile Scalpellum-Art 

 aus dem Schlier vou Ottnang uud Kremsmiiuster, sowie iiber Cirripedien 

 im AUgemeinen," Jalirbuch der k. k. geolog. Reichsanstalt, 1887, 37 Bd., 

 p. 37(3. 



t A. Pagenstecher, " Untersucliungen iiber niedere Seethiere aus 

 Cette. — IX. Beitrag zur Aiiatomie uud Eutwickluugsgeschichte von 

 Lepas pectinata,'^ Zeitschr. f. wiss. Zool. Bd. 13, 18G3. 



X C. Claus, "Die Cypris-ahnliche Larve (Puppe) der Cirripedien und 

 ihre Verwaudlung in das festsitzende Thier," Schriftender GeseUsch. zur 

 Befdrderuug der gesammteu Naturwiss. zii Marburg, Supplementlieft v., 

 1869. Also ' Uutersucliungeu zur Erforscliung der genealog. Grucdlage 

 des Crustaceensystems,' pp. 79-88. 



