258 NATURAL HISTORY. 



lets itself down from the leaves by one. The Marine Planaria are found swimming in an undulating 

 manner on the surface of the ocean, where they seem to live free. Darwin described one in 1844. 

 Moseley describes them, in the East Indian Archipelago, as swimming in a lively manner. Others 

 collect on the Gulf Weed ; such are the Stylochidse, which have two small tentacles with eyes on 

 them and on the head also. They swim in a rapid sinuous manner, and attack their prey at once. 

 In this group the young undergo a metamorphosis, and in one stage greatly resemble a Rotifer. 



The Nemertina are long, worm-like, proboscis-bearing, and marine ; they have brittle bodies and 

 a straight intestine with lateral cseca. The body is very extensile, and they live under stones, avoid 

 light, and hunt their prey. 



The Sea Long Worm (Lineus longissimus) is fourteen feet long and only two to four lines broad. 

 The eggs of these give forth ciliated embryos, and they grow into a helmet-shaped body with a tuft 

 of cilia. Certain cells enclose the digestive canal and give rise to a worm-shaped body the future 

 adult form. This fact links the group to the Echinoderms. 



Worms lived in the geological ages, and certain markings in the old rocks are attributed to 

 them. Trails and tracks of the Errantia, such as are termed Kereites and Phyllodocites, are found 

 in the Silurian rocks. The horny jaws of the Errant Annelida have been found in the Palaeozoic 

 formations, and largely in the upper Silurian of Wenlock. Burrows of worms occur in the Cambrian 

 and Silurian age, such as Scolithes and Arenicolites, and the casts or the faecal matters of Annelida, 

 are frequent in many rocks. Tubicolar Annelida of the extinct genera Cornulites, Ortonia, Ser- 

 pulites, Spirorbis, Serpula, &c., are found from the Silurian to the latest geological deposits, but 

 the gensra usually became extinct with time, the last two still existing. 



CLASSIFICATION. 



TYPE VERMES. 



( Order Oli<?oeha3ta. 



CLASS ANNELIDA .... Sub-class Chaetopoda 



,, I olychceta. 



Hirudinea . . ... 



/ ., Gephyrea Inermia. 

 GEPHYREA ......... ,, Armata. 



Tubicola. 



Family Philodinidte. 

 T, \ Brachionidse. 



., ROTIFERA ......... 



I Hydatineae. 

 * ,, Floscularidas. 

 NEMATHELMINTHA ........ j Order Nematoidea. 



( ,, Chaetognatha. 

 ( Cestoida. 



PLATHELMI*THA - . > \ Trematoda. 



Turbellaria. 



P. MARTIN DUNCAN, 



