Q 



49 



characteristic, specimens having been obtained from a depth 

 of 4,000 fathoms off Teneriffe. ("Challenger.") Otherworms 

 also occur. Even species of the same genus have a widely 

 varying distribution in depth. Thus, the tubicoloid genus 

 Spirorbis has its littoral species growing within the shore 

 zone; while another species. S. n;iutUoides, has been dredged 

 at a depth of 700 fathoms. Similarly, the Gepkyrean Phas- 

 colosoma is represented along our northern shores by a 

 species living in the mud and sand above low tide, while the 

 "Blake" brought up a species in a Dentalium shell from a 

 depth of 1,568 fathoms.* 



Among the Annelids the family Eunicidae is of particular 

 interest, in that its several members are characteristic of 

 different bathymetric zones, thus furnishing, in a measure, an 

 index to the bathymetric po.sition of the fanna which they 

 characterize. This family is well represented in the litho- 

 graphic shales of Bavaria. (Ehlers.) Among the worms, 

 regeneration of lost parts, and generation of new individu- 

 als from fragments of old ones, is not uncommon. Thus in 

 one of our common pelagic worms — Autolytus — swimming 

 buds carrying the sexual products are periodically con- 

 stricted off, each regenerating a new head, with highly 

 developed eyes, at the anterior end. The earth worm — 

 Lumbriusc — falls into pieces in autumn, all of which are 

 able to regenerate into complete animals.f 



A mero-planktonic ciliated larva, the Trochophore, is 

 characteristic of worms, this being the product of a sexual 

 mode of reproduction. These larvae are often obtained in 

 vast numbers in the tow-net, together with other mero- 

 planktonic and many holo-planktonic forms. 



Bryozoa. — The Bryozoa are marine or fresh water, chiefly 

 colonial, benthonic animals. A few occur parasitic on a 

 living substratum, but the majority of species are epiphy- 

 tically attached to organic or inorganic objects, either 

 basally or in an encrusting manner. The majority of species 



*Agassiz, '88, II., 53. 



t Lang, A.— Text book of Comparative Anatomy. 



