ON THE ANGUILLULIDyE. 89 



of these minute Nematodes, wliicli gives some parts of the flower a white filamentary 

 appearance. They seem to be endowed with the same tenacity of life as Tylelenclms tritici, 

 and, from their correspondence in anatomical details, evidently belong to the same genus. 

 Whilst speaking of these parasites of vegetables, I may again mention the fact that two 

 or three of the most highly organized species of the free Nematoids I have met with, 

 all the specimens of which are provided with well-developed ocelli, have been found 

 infesting some of the British marine Sponges. Although there can be no doubt of the 

 animal nature of these latter, still the organization of Sponges is so peculiar that the 

 conditions of existence of these minute Nematoids within their interstices may, on the 

 whole, be considered much more nearly allied to those of the non-parasitic Nematoids 

 in general than to those to which the parasitic forms are subjected within the various 

 organs of more highly developed members of the animal kingdom. There would seem 

 to be no more reason why these animals should be considered parasites on account of 

 their habitat, than that those Annelids with which they are often associated in the 

 Spongiadcs should, for a like cause, be brought under the same designation. 



Classification. 



The only two writers who have attempted to classify the free Nematoids are Diesing 

 and Eberth ; and since the opinions of both are so much entitled to respect, it will be only 

 right for me to consider their respective schemes of classification, and point out, not 

 only the nature of these schemes, but also in what way they appear to me to be defective. 



Diesing's most recent communication is to be found in a paper entitled " Revision der 

 Nematoden'", in which he treats of the classification of the Nematoids generally. I shall, 

 of course, confine my attention to what he has to say on the free Nematoids. These, 

 with one or two other genera of a doubtful nature, he includes under two families, 

 the distinguishing characters of which he considers to be the presence or absence of 

 cirrhi or setae around the mouth. His arrangement is as follows : — 



Family I. Cirrhostomea. Corpus capillare. Os terminale cirrhatum. Ocellata vel c^ca. Penis 

 baud vaginatus v. vagina tubulosa exceptus. Papilla suctoria caudalis nulla v. unica terminalis. Ani- 

 malcula ut plurimum microscopica. Aquarum dulcium vel maris incolse. 



* Ocellata. 

 1. Phanoglene. 2. Enchelidium. 



** Cceca. 

 3. Pontonema. 4. Amblyura. 



t 



Family II. Anguillulidea. Corpus capillare, inerme vel armatum. Os terminale sessile, v. in 



apice tubuli protractilis, inerme aut denticulatum, nudum vel papillis cinetum. Casca, rarius ocellata. 



Penis baud vaginatus aut vagina dipetala inclusus. Papilla suctoria caudalis nulla vel unica terminalis 



vel duEe marginales. Animalcula minora. Aquarum dulcium vel maris incolae, aut in ahimalibus variis 



endoparasita, nonnulla migratoria. 



* Odontostomata. Os dentatum. Cceca vel ocellata. 

 t Ocellata. 

 5. Enoplus. 



' Sitzungsb. der Kais. Akad. der Wissensch., xlii. Band, No. 28, p. 595. 

 VOL. XXV. N 



