Introduchon to Animal Morphology. 155 



Province i. Archteostomata* [Huxley), 



Class i. Turbellaria [Ehrcnicrg). — Unjointed, 

 rarely parasitic, ciliated, leaf- or ribbon-like worms, 

 rarely with chitinous processes or bristles (not arising" 

 in follicles), or circlets of stronger cilia (Dinophilus). 

 The integument consists of cells or of undivided pro- 

 toplasm, containing, in the aquatic forms, nettle-cells 

 scattered or clustered ; sometimes rod- or spindle-like 

 bodies, with (Meckelia) or without appended threads 

 may exist in capsules, like those of the true nettle- 

 cells (absent in Geoplana, ScJiultzc). 



The integument may also contain chlorophyll (Vortex 

 viridis, Convoluta Schultzii) or calcareous concretions (Sidonia 

 elegans). The component plastides are best seen in land 

 planarians, where the glandular elernents are divided into 

 superficial and deep. The sub-cutaneous muscular layer 

 consists of usually three laminae, an outer circular, well marked 

 in Bipalium and Dendrocoelum, often undifferentiated in 

 others, a middle, longitudinal (the strongest), and an inner 

 circular.! The fibres in most are but spindle-cells loosely 

 scattered in a net-work of connective tissue (except in Ne- 

 mertinea). 



Cotylidse, or united to Chsetopoda to form a group Annelida. Rotatoria 

 is placed by many among the Arthropods near Crustacea. Bryozoa and 

 Tunicata are usually and naturally united to Brachiopoda to form a sub- 

 division MoUuscoida, but as the MoUusca proper are only an extreme of 

 specialization of this sub-division of Vermes, it would be still more natural 

 to add them all together in the one sub-lungdom. However, as for con- 

 venience we retain the specialized group separately, it is to a large extent 

 arbitrary where the line of demarcation is drawn ; so, though many eminent 

 zoologists, as Lankester, prefer to retain the Tunicates, &c., with the 

 Molluscoids, I have followed Gegeiihaiir in my classification. 



* These characters (p. 47), being primary embryonic ones, should over- 

 ride the sub-kingdom characters here adopted ; but in the present condition 

 of our knowledge, we can scarcely apply them to all the included forms. 



t Among Nemerteans, these varj' in their arrangement. 



