412 Dr. 0. A. L. Morch on the Limits 



the Arthropoda, contained only a single true intestinal species 

 (the Endoconcha of John Miiller), whilst the "Entozoa" have 

 contributed considerably to the Arthropoda^ viz. Lernaia, Pelto- 

 gaster, Clistosaccus, Linguatula. 



The Helmintha are generally divided into two sections, — viz. 

 Nematodes with distinct sexes, and Platyhelmia with the sexes 

 united. Mr. Bastian* has, at the last meeting of the lloyal 

 Society, on the 15th of June, pointed out that the Nematodes, 

 parasitic and free, are closely allied to the Echinodermata. 

 The Platyhelmia, containing the Trematoda, Cestoda, and Tur- 

 bellaria, seem to me not to differ materially from the androgy- 

 nous Mollusca. 



The Turbellarians are united to the Mollusca by Mr. Ch. 

 Girardf, on account of the resemblance of the embryonic state 

 of Planocera elliptica with that of Elysia. It must, however, be 

 remembered that the " chrysalis^' state is not known among the 

 Mollusca, and that all larva; of Gasteropoda are provided with a 

 nautiloid shell, except the larva of Chiton. The Turbellarians 

 differ chiefly from the Gasteropoda in the presence of numerous 

 eyes ; but this difference is perhaps not of great importance, as 

 Dr. Bergh has discovered four eyes in a species of Fidiana from 

 St. Thomas, and AgassizJ indicates that Margarita is provided 

 with eyes, at the base of the pedal filaments, corresponding to 

 those in the mantle-edge oi Pecten and other Acephala. Dr. 

 Bergh, however, has not found any lens in the " eyes " of the 

 pedal filaments in Margaiita. According to Prof. Hensen, the 

 lens is absent in Nautilus. 



The nervous system shows no important difference from that 

 of Gasteropoda. The want of a true foot is of no consequence. 

 In Bulla^, Akera, &c., the locomotion is partly, and in Pelli- 

 branchiata almost entirely, effected by the hind part of the body, 

 the true foot being reduced to a crescent-like disk, not unlike 

 the sucker in many Entozoa. The arborescent form of the in- 

 testinal canal, generative organs, and kidneys is common to 

 all animals wanting special respiratory organs. 



Salivary glands are present, but the liver is entirely absent, as 

 is usually the case in animals [e.g. perfect Insects) living upon 

 food not requiring preparation. The Tanice want even a mouth 

 and intestinal canal, living in a prepared nutrimental juice, 

 which the parasite absorbs through the surface of its skin; a 



* The AthenBeum, June 1865, p. 850. [Anuals for September, 

 p. 197.] 



■y Researches upon Nemertians and Planarians. Philadelphia, 1854. 



X Lectures on Embryology, p. 86, 8vo. 



§ Morcb, " Contributions a la Faune malacologique des Antilles 

 danoises," Journ. de Conch. 1863, p. 19. 



