CH^TOGNATHA. 357 



beetles and other aquatic predatory insects eat with the flesh of the Ephcmcrid 

 larva the encysted young forms, which then develop in the body cavity of 

 their new and larger host to young Gordlidce. Gordius aquaticus Dvj. 



Fam. Anguillulidae. * Free living Nematodes of small size. Caudal 

 glands are sometimes present. The lateral canals are often replaced by the 

 so-called ventral glands. Some species either live on or are parasitic in plants ; 

 others live in fermenting or decaying matter. The greater number, however, 

 live free in earth or water. Tylenchus Bast. Buccal cavity small, and con- 

 taining a small spine. The female genital opening lies far back. I\ scandens 

 Schn. = tritici Needham, in mildewed wheat grains. When the grains of wheat 

 fall the dried embryos grow in the damp earth, bore through the softened 

 membranes, and make their way on to the growing wheat plant. Here they 

 remain some time, perhaps a whole winter without alteration, until the ears 

 begin to be formed. They then pass into the latter, grow, and become 

 sexually mature, while the ear is ripening. They copulate and deposit their 

 eggs, from which the embryos creep out, and at length constitute the sole con- 

 tents of the wheat grains. T. dipsaoi Kuhn, in heads of thistles (Cardius) 

 T. Davainii Bast, on roots of moss and grass. Heterodera Schachtii Schmidt., 

 roots of the beet-root, also of the cabbage, of wheat, barley, etc. Rhabditis 

 Duj., divided by Schneider into Lcptodera Duj. and Pelodera Schn. Rh. 

 flexilis Duj., head very sharply pointed, mouth with two lips, in the salivary 

 glands of Limax cinereus. Rli. anglostoma Duj. RJi, appendiculata Schn., 

 in damp earth, 3 mm. long. The larva, which is without a mouth, and has two 

 caudal bands, is found in Arion empiricovum. Angnillula aceti = gliitinis 

 0. Fr. Mull., known as the vinegar worm and pasteworm, 1 to 2 mm. long. 



Of the many marine Angmllulidce {Enoplidaf), we must mention Dory- 

 lalmus maximus Butschli, D. stagnalis Duj., found in mud everywhere in 

 Europe. Enclielidiwm, marinum, Ehrbg., Enoplus trldentatus Duj. 



The abberant families Desmoseolecidce and Chcetosomidce are allied to the 

 Nematoda. 



THE CH^ETOGNATHA. 



The Chcetognatha, f containing only the genus Sagitta, are allied 

 to the Nematodes. They are elongated round worms, with a pecu- 

 liarly armed mouth and laterally placed horizontal fins, the mem- 

 branous edges of which are supported by rays. The anterior 

 portion of the body is sharply separated off as a head, and bears in 



* Davaine, " Recherches sur I'Anguillule du ble nielle," Paris, 1857. Kuhn, 

 " Ueber das Vorkommen von Anguillulen in erkrankten Bliithenkopfen von 

 Dipsacus fullonum," Zeltschr.fur wiss Zool., Tom IX., 1859. Bastian, " Mono- 

 graph of the Anguillulidae or free Nematoids, marine, land, and fresh water," 

 London, 1864. O. Butschli, ' Beitrage zur Kentniss der freilebenden Nema- 

 toden," Nov. Acta, Tom XXXVI., 1873. Lad. Oerley, "Monographic der 

 Anguilluliden," Buda-Pest., 1880. 



f Compare A. Krohn, " Anatomisch-physiologische Beobachtungen liber die 

 Sagitta bipunctata," Hamburg. 1844. R. Wilms, " De Sagitta mare germani- 

 cum circa insulam Helgoland incolente," Berolini. 1846. Kowalevski, "Em- 

 bryologische Studien an Wiirmern und Arthropoden," Mem. de VAcad. 

 St. Petersburg, Tom XVI. 0. Hertwig, " Die Chsetognatha, eine Mono- 

 graphic," Jenr,, 1830. 



