ENTOZOA. 



[ 234 ] 



EPENDYMA. 



In numerous instances, after this primary 

 stage of development — the embryonal ceil 

 condition — has been attained, the embryo 

 does not become directly developed into a 

 form of being resembling the parent, but the 

 intermediate larval or nurse forms, described 

 under Alternation of Generation, are 

 produced from it by a non-sexual process, 

 and ultimately, forming the last stage of the 

 metamorphosis, beings resembling the parent 

 and furnished with sexual organs are pro- 

 duced. The discovery of the alternation of 

 generation has brought to light the fact that 

 many of the supposed species of Entozoa 

 are only the larval or nurse forms of the 

 true species ; and that many of these forms 

 only complete their stages of metamorphosis 

 when placed under particular circumstances. 



The following arrangement may serve as 

 an index to the articles upon the Entozoa, 

 contained in this work : — 



Order 1. Sterelmintha. Alimentary canal 

 often absent, or not distinct; when present, 

 with a single orifice only, and branched. 



Fam. 1. Cestoidea (tape-worms). Body 

 strap-shaped, distinctly or indistinctly 

 divided into transverse joints; male and 

 female organs in each joint; alimentary 

 canal doubtful or indistinct. 

 Bothriocephalus, Tcenia. 

 {Cystica) Nm'se or larval forms of 

 Cestoidea. 

 Fam. 2. Trematoda. Body mostly flat- 

 tened ; alimentary canal distinct, 

 branched ; male and female organs in 

 each individual. 



Ampliistoma, Dij)lozoon (Diporpa), 

 Distoma. 

 Fam. 3. Acanthocephala. Body flatten- 

 ed, transversely wrinkled, becoming 

 cylindrically distended by the imbibition 

 of water ; sexual organs in separate 

 individuals. 



(Echinorhynchiis.) 

 Fam. 4. Gordiacea (hair-worms). Body 

 filamentouSjCylindrical, alimentary canal 

 present ; sexes separate. 

 Gordius, Mermis. 

 Fam. 5. Protozoidea or Gregarinida. 

 Probably larval states of some other 

 organisms. 

 Gregarina. 



Order 2. Coelelmintha. Alimentary canal 

 present, distinct, simple, with two orifices. 



Fam. 1. Nematoidea (round worms). 



Body cylindrical, hollow; sexes sepa- 

 rate. 



Anguillula, Tricoceplialus, Filaria, 

 Ascaris {Oxyurus), ? Trichina. 



See Acephalocysts. 



BiBL. Siebold, Vergleich Anaf. Ill, and 

 Ann. d. Sc. nat. 3rd ser. Zool. xxvi. p. 376 

 Rudolphi, Entozoor. Hist, nat., and Entoz 

 Synops. ; Dujardin, Hist. nat. d. Helminth 

 Cloquet, Anat. d. verslntest.; Wedl, Grundz 

 d. Path. Anat.; Bremser, Icones Helminth. 

 Owen, Todd's Cycl. ii. 11 1 ; Blanchard, Ann 

 d. Sc. nat. 3rd ser. Zool. vii. viii. x. xi. xii, 

 Vogt, Ann. Nat. Hist. 2nd ser. ix. 437 

 Beneden, Les vers Cestoides, 1850 ; id. 

 Ann. d. Sc. nat. 1851. 3rd ser. xvii. 23 

 (Trematoda) ; id. Prize Essay (not yet 

 published), abstract in Cosmos, iv. 267 and 

 382 ; ibid. Kuchenmeister ; Siebold and 

 Bilharz, Sieh. and Kollik.'s Zeits. iv.; Crep- 

 lin and Gurlt, Wiegmann's Archiv, 1845- 

 1851; V. d. Hoeven, Handb. d. Zool. i. 154. 



EOSPHORA, Ehr.— A genus of Rotatoria, 

 of the family Hydatinsea. 



Char. Eyes three, sessile, two frontal, one 

 cervical ; foot forked. Aquatic. 



There are three species. 



E. digitata (PI. 34. figs. 28 ; 29, teeth). 

 Body conical, hyaline, not auricled, toes 

 one-third of the foot in length. Length 1 -96". 



BiBL. Ehr. Infus. p. 451. 



EPE IRA, Walck. — A genus of Arachnida, 

 of the order Araneidea. 



E. diadema (the common autumnal 

 garden-spider) forms a favourable object 

 for the examination of the various structural 

 peculiarities of spiders ; as the integument 

 (PI. 2, fig. 4) ; the legs, with their hairs and 

 claws (figs. 8, a, b,) ; the toothed hairs at 

 the end of the feet (fig. 8) show^ very clearly 

 the transition from the hairs to the claws ; 

 in fact, that the latter are mere modifications 

 of the former ; also the lung-plates (figs. 9, 

 9 b) ; the spinnerets, the web (fig. 11), &c. 



BiBL. Walckenaer, Hist. nat. d. Apteres; 

 Cuvier, new dateless edition; Brandt, 

 Medizin. Zool.; V. d. Hoeven, Handb. d. 

 Zool. i. 573. 



EPENDYMA VENTRICULORUM — 

 Is the name given to a layer which coats 

 those portions of the ventricles of the brain 

 which are not connected with the prolonga-' 

 tions of the pia mater ; as the floor of the 

 fourth ventricle, the aqueduct of Sylvius, 

 the floor and the sides of the third ventricle, 

 the ventricle of the septum lucidum, with the 

 roof, the anterior and posterior cornua and a 



