ON THE ANGUILLULID^. 75 



rewarded by the most gratifying results — more especially as, with the exception of the 

 " Paste" and " Vinegar Eels," the Vibrio tritici, and one or two unknown species always 

 alluded to by the same name of Anguillula fluviatilis, no representatives of this group 

 have, I believe, yet been described as existing in Great Britain : hitherto the harvest 

 has been with the continental naturalists, with Dr. Leidy in America, and with our own 

 countryman Carter in India. 



As a result of my investigations, I am inclined to believe that these free Nematodes 

 will be found to constitute one of the most widely diffused and nvimerically abundant 

 groups in the whole animal kingdom, rivalling, in the first respect at least, the almost 

 ubiquitous Diatomacese. A statement of some of the principal situations in which I have 

 met with these animals will best illustrate this proposition. Thus, beginning with the 

 land- and freshwater-species, I have found them in all the specimens of soil examined, in 

 moss, various species of lichen, about the roots of fungi ^, also the roots of grasses, and 

 between the sheaths of their leaves, amongst the mud of ponds and rivers, on the fresh- 

 water Algse, amidst decaying liverworts and mosses, and on submerged aquatic plants- 

 The marine species exist in great abundance in the surface-mud of rivers and estuaries ^, 

 in the sand, and amongst the small stony debris under the shelter of rocks, as well as in 

 the tide-pools, where they swarm about the roots of the corallines and on some of the 

 smaller and finer sea-weeds, especially those having a dingy appearance from the pre- 

 sence of Diatomacese. And, lastly, two or three species I have found in the greatest 

 abundance, as pseudo-parasites, within the substance of some of the softer sponges. So 

 numerous are they in these latter situations, that it is rather surprising they should have 

 so long escaped the attention of marine zoologists. Erom the transparency of their in- 

 teguments, they are not only beautiful microscopical objects, but also admirably adapted 

 for anatomical research ; and Dr. Eberth and myself have already worked out so many 

 interesting structural details, that I have no doubt, should the investigation be followed 

 up by other observers, the question of the anatomy and real affinities of the Nematoids, 

 at present so doubtful, would be soon placed tipon a satisfactory footing. 



The specimens I have examined have varied in length from y^" to nearly f ", almost all 

 the larger forms being marine, though Dorylcdmns staynalis, Dujard., is about \" long, 

 and far exceeds in size any of the other land or freshwater species I have met with. In 

 their various habitats individuals of aU ages may be seen, from the young, immature and 

 non-sexual embryo just emerged from the egg or its parent, up to the adult condition ;■ 

 and frequently the ova of species infesting a particular sea-weed may be seen attached 

 to it, whilst the parent worms are gliding and twining, serpent-like, amongst its branches. 

 This fact alone would induce one to believe that these animals are never parasites at any 

 stage of their existence, even if this view were not- confirmed by the existence of ana- 

 tomical peculiarities which seem to distinguish them as a group from the parasitic forms 



^ I have not been very successful in finding these animals on or in fungi, though Carter has discovered them in 

 abundance at Bombay projecting from the couceptacles of a large species of the genus Xylaria, growing on the decayed 

 trunk of a tamarind-tree. (Trans, of Med. and Phys. S^ of Bombay, 1861, App. p. 1.) 



- I have found six different species existing, more or less abundantly, in a small portion of mud that could be held 

 on a shilling piece. 



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