Dr. Morch on the Limits of the Suhkingdom Mollusca. 41 1 



XLVI. — On the Limits of the Suhkingdom Mollusca. 



By Dr. 0. A. L. Morch. 



The Vertebrata form the only subkingdom with uncontroverted 



limits ; yet the late Prince Bonaparte considered the Aphanozoa 



[Sagitta, &c.) the lowest Vertebrata. 



Since the time of Cuvier^ the Tunicata have been considered 

 by zoologists true Mollusca. Professor Huxley has shown that the 

 Bryozoa are inseparable from the Tunicata. The Brachiopoda 

 are considered allied to the former, thus forming the subclass 

 Molluscoidea of several modern authors. Dr. Macdonald* has 

 lately added the Ctenophoraf to the Brachiopoda J. 



Prof. Loven first raised a doubt as to the affinity of the Tuni- 

 cata to the Mollusca, chiefly on account of the form of the larva 

 of Ascidians. Dr. Macdonald founded the same doubt chiefly 

 on the reproduction by budding, which is foreign to the nature 

 of Mollusca. This reason alone cannot be considered sufficient, 

 as there is found in nearly every class a division (subclass, mi- 

 crosthenic division) diff^ering in having an abortive progeny, e. g. 

 Marsupialia, Amphibia, Orthoptera among Mandibulata, and He- 

 miptera and Homoptera among Haustellata, Entomostraca, &c. 



The systematic position of the Tunicata seems chiefly to be 

 based on a supposed resemblance between the two apertures of 

 Ascidians with the siphons of Acephala, and a still more super- 

 ficial resemblance between " the shells." 



Another division, containing gelatinous and arborescent forms 

 (the Acalephse), seems to have a much greater affinity to the 

 Acephala, with which they agree in the four labial palpi and the 

 fringed oculiferous edge of the mantle. This resemblance is 

 very striking if the Acaleph be compared with a swimming 

 Lima, as mentioned by Sars. The radiated form indicates the 

 same relation to Acephala as Cephalopoda bears to Gasteropoda. 

 The group Radiata as defined by Cuvier do not really exist. 

 Cnidse and phlebenterism are found in the Gymnobranchia to a 

 great extent, being dependent on the want of a shell §. The An- 

 thozoa, considered inseparable from the Acalephse, look no 

 stranger among the Mollusca than the Bryozoa. 



There are, however, some other Coelenterata which may be 

 referred to the Mollusca with still more precision. I have 

 always thought it strange that the Mollusca, although inferior to 



* Transactions of the Royal Academy of Edinburgh, 1864. 



t Miirch, Fortegnelse over Gronlaads Bloddyr, 1857; Rink, Gron- 

 land, p.97. 



X Malacozoologische Blatter, vi. p. 104. 



4 In Cyanea is found a brown membrane reminding us of the Loligo- 

 shell. 



