Marine Animal Forms in Fresh Water,' ^' 61' 



only^' ^Jiesc^iitjr division of the Merostoma {Limulus)^t'\ie'i[i6ki" 

 noi^tliern of which occurs near Boston. 



Of the essentially aquatic classes (or subclasses, according W^ 

 the differences of system) of animals, we find that eleven, namely 

 the Polycystinese, Anthozoa, Acalephse, Ctenophora, Siphono- 

 phora, Echinodermata, Tunicata, Brachiopoda, Pteropoda, Hete- 

 ropoda* and Cephalopoda are exclusively marine, and the same 

 number, namely, besides the forms already referred to, the Infu- 

 soria and Rhizopoda, the Hydroid polypes, Rotatoria, Bryozoa, 

 Turbellaria, and Annelida, are common to both media, amongst 

 which, however, the very numerous sections are purely marine 

 (Sertularina, Bryozoa Stelmatopodaf, and the numerous, very 

 highly developed order of the Annelida), whilst the sections 

 proper to the fresh water are less rich in species, like the 

 freshwater Polypes and Bryozoa [Hydrina and Bryozoa Lopho- 

 poda) and the Plauarics in the most restricted sense. 



The Batrachia furnish the only example of a class of animals 

 which is entirely wanting in the sea, and yet they are water- 

 breathers, at all events temporarily : we are acquainted with ma- 

 rine Tortoises, marine Lizards (Darwin^s Amblyrhynchus cristatus 

 upon the Galapagos Islands), and marine Snakes [Hydrophis), 

 besides the notorious Norwegio-American one, but, in spite of 

 Seba and Schiller^s ' Taucher^ not a single Sea Toad or Sea Newt. 

 Of the strictly air-breathing classes, lastly, certain representatives 

 live constantly in the sea ; of the Birds and Insects only a few 

 venture temporarily into and under the w^ater, both fresh and 

 salt, but live essentially above its surface J ; amongst Insects, we 

 have here especially the small, apterous, Carabideous Beetle 



[* The author has previously regarded the Heteropoda as forming a 

 portion of the class Gasteropoda. — Transl.] 



t According to Dumortier and Van Beneden, however, the freshwater 

 genus Paludicella belongs to this group. — [According to Professor Allraan 

 (' Monograph of the Freshwater Polyzoa,' Ray Society, 1856), both Palu- 

 dicella and Urnatella, although freshwater genera, belong to the group 

 above mentioned ; whilst on the other hand, the marine genus Pedicellina 

 appears to have a bilateral lophophore, which would cause its location 

 amongst the fresliwater forms. Fredericella also, a freshwater genus, pos- 

 sesses a funnel-shaped lophophore. Professor AUraan's classification, in 

 which the two orders of Polyzoa are distinguished by the presence or 

 absence of an epistome, or lobe in the vicinity of the mouth, does not get 

 rid of this appearance of marine forms in fresh water and vice versa. — 

 Transl.] 



[J The author here seems to have forgotten the existence of whole fami- 

 lies of Beetles and Bugs, which live habitually beneath the surface of the 

 fresh water, whilst the larvae of many of the former are even adapted to 

 aquatic respiration. The larvae of a great proportion of the Neuroptera 

 also are strictly aquatic, and those of many Diptera live in water, although 

 most of them breathe au\ — Transl.] 



