cobb: draconema 145 



HELMINTHOLOGY. — Draconema: A remarkable genus of ma- 

 rine free-living nematodes. N. A. Cobb, Bureau of Plant 

 Industry, Communicated by Frederick V. Coville. 



Few nematodes, if any, are more remarkable than Draconema. 

 From a comparative anatomical point of view it takes rank with 

 the bifurcated Lepidonema. The main features of Draconema 

 are illustrated in the adjacent cut. Though the head end is very 

 peculiar, all its peculiarities are more or less comprehensible. 

 While the cephalic setae, amphids, mouth, oesophagus, and car- 

 dia, all present singular features, yet these features are referable 

 to known types of nematode anatomy. Even the sudden loss in 

 diameter behind the oesophagus, tho unique, is understandable 

 on the supposition that unusual flexibility is required in this 

 region owing to some odd habit of life. 



In contemplation of the remainder of the anatomy, however, 

 one becomes lost in amazement, and can only speculate on the 

 nature and function of the complicated longitudinal series of 

 lateral and sub ventral appendages. These appendages are found 

 fully developed on both sexes, young or adult, and must, therefore, 

 have to do with functions exercised at various stages of growth, 

 and without regard to sex. 



As we know little of the habits of Draconema beyond the fact 

 that it occurs on or near red marine algae of strands in various 

 parts of the world, speculation concerning the functions of its pecu- 

 liar organs may be idle. One might suggest that the form of the 

 body indicates possibly that the species inhabit tubes, which they 

 may be imagined to construct, or which they may find already 

 constructed and adapt to their uses. The existence of such a ' 

 dwelling would harmonize with the expanded head and with the 

 slimness of body behind the neck. Supposing the head end to 

 be thrust out of the tubular home, the advantages of a limber 

 body in seeking food can be readily understood. So too, the 

 series of tubular organs might fit in with such a confined habit 

 of life, and have to do with the construction and repair of the 

 supposed tube; or with locomotion; or with aeration, by producing 

 currents of fresher water inside the tube. 



