^164. 



THE ANNELIÜES. 



177 



vitellus is usually whitish or yellowish, but rarely of a more marked 

 color/^^ 



With the Hirudinei and Lumbricini, the spermatic particles are filanien- 

 toid and very active, while with the other Annelides they have the form of 

 Cercariae.^*^ 



§164. 



With the Hirudinei, and Lumbricini, the two sexes are always jnited m 

 the same individual. The sexual organs consist of testicles, vasa deferen- 

 tia, and vesiculae seminales ; then, ovaries, oviducts, and the male and 

 female copulatory organs. The female copulatory organs are upon the- 

 ventral surface of tlie anterior part of tlie body and behind the male 

 organs — so that two individuals by placing together their anterior ventral 

 surfaces in an inverse position, can be mutually impregnated.*^' 



The excretory ducts of both sexes are often lined with a very delicate 

 ciliated epithelium. 



from the eggs of other Annelides, in containing be- 

 tween the vitellus and vitelline membrane a layer 

 of caudate cells. These cells, of variable numlier 

 and size, but always of uniform size in the same 

 egg, have often been compared, from their form, to 

 Naviculacae ; see Henle, in Mu/ler''s Arch. 1835, 

 p. 591, note, and Hojf'meister, De vermibus qui- 

 busdam, &c., Tab. II. fig. 14-17. 



3 The vitellus is rose-colored, or greenish, with 

 Clepsine, and violet with Polynoe. 



■4 The development of the spermatic particles of 

 the Hirudinei and Lumbricini is very remarkable. 

 The cell-membrane of the parent cells, in which the 

 spermatic particles are usually developed, disap- 

 pears before these last are developed. There are then 

 small cells groui)ed around a discoid nucleus. These 

 cells lengthen out, and finally become spermatic 

 particles, and they remain attached to the disc until 

 fully developed. If a bundle of these is placed 

 in water, they separate and become intertwisted in 

 the usual manner ; see Henle, in Müller\i Arch. 

 1835, p. 584, Taf. XIV. fig. 4, 6, 7, 9 ; Kolliker, 

 Beitr. zur Kenntn. d. Geschlechtsverliftltnisse, p. 

 17, Taf. II. fig. 16, 18, 19 ; H. Meckel, Mailer's 

 Arch. 1844, p. 477, Taf. XIII. fig. 2-10 (Sangui- 

 suga, Pontobdella, and Branchiobdella) ; and 

 Hoffmeister, De vermibus quibusdam, &c.. Tab. 

 II. fig. 6-10. From 5fannt'u.s' description and fig- 

 ures of the sperm of Arenicola (Muller''s Arch. 

 1840, p. 375, Taf. XI. flg. 3-6); and Ratliki ofthat 

 of Amphitrite auricoma (Danzig. Schrift, loc. cit. 

 p. 67, Taf. V. fig. 13) ; and Quairefai^es, of that 

 of Nemertes mandilla (Rögneanim. illustr. Zooph. 

 PI. XXXIV. fig. 3-5), we can conclude that the 

 spermatic particles of the other Annelides are de- 



* [ §. 163, note 4.] For the spermatic particles 

 of the Hermella, see Quatrefages (Ann. d. Sc. 

 Nat. X. 1848, p. 167) ; he describes them as being of 

 a cercaria-form. My own results on the spermatic 

 particles of the Annelides and their development, 

 do not agree with the view above expressed. Here, 

 as elsewhere, I have found them to be the metamor- 

 phosed nucleus of the daughter-cells. It is true 

 that with the Lumbricini they present some pecu- 

 liarities, but these are apparent only. The mul- 

 berry-like mass to which they are here found ad- 

 herent, is composed of the remains of the develop- 

 ment, and the spermatic particles which seem to ra- 

 diate from it in all directions present this appear- 



veloped like those of the Hirudinei and Lumbricini. 

 While in the excretory ducts of the sperm, the 

 spermatic particles are found in bundles ; and when, 

 as at the procreative period, many of these bundles 

 are collected together, their very active, undula- 

 tory movements give a most wonderful appearance 

 beneath the microscope ; see Morren, loc. cit. p. 

 178, Tab. XXIV.-XXVIII., and myself in Muller's 

 Arch. 1836, p. 42. Among the filamentoid sperm- 

 atic particles of Hirudinei, those of Branchiob- 

 della are worthy of special mention. One of their 

 extremities is delicate and spirally turned (see my 

 observations, Muller's Arch. 1836, p. 42, Taf. II. 

 fig. 8), and terminates, according to Kolliker, by a 

 small vesicle (Iw. cit. p. 18, Taf. II. fig. 16, f.).. 

 With the Branchiati, the cercarian-form predomi- 

 nates, according to (Quatrefages (Comp. Rend. 

 XVII. 1843, p. 424). With the Nemertini, they are 

 either simply filamentoid (^Nolospermus, accord- 

 ing to Orsted, Entwurf, einer Einth. d. I'lattwiirm. 

 loc. cit. Taf. III. fig. 54) or more cercarian-fornv 

 (Nemertes, according to Quatrefages, Regne 

 anim. illustr. Zooph. Fl. XXXIV. fig. 6 ; and Kol- 

 liker, Verhandl. d. Schweiz, naturf. Gesellsch. bei 

 ihrer Versammlung zu Chur. 1844, p. 91). 



For the spermatic particles of the Annelides, see 

 especially Kolliker in the Neue Schweiz. Denkschr. 

 VIII. p. 33.* 



1 See Bojanus, Isis, 1818, Taf. XXVI. fig. 1 ? 

 Brandt, Med. Zool. II. Taf. XXX. fig. 25 (Sangui- 

 suga medicinalis) ; Leo, Muller's Arch. 1835, 

 Taf. XI. fig. 3 (Piscicola geometra) ; Morren^ 

 loc. cit. Tab. XXVII.-XXXI.; and Hojfmeister, 

 De vermibus quibusdam, &c., Tab. I. fig. 29, 3* 

 (Lumbricus and Enchytraeus).\ 



ance because they are then just escaping from the 

 daughter-cells, and the more or less adherence of 

 the membrane of these last to the particles, gives 

 the appearances above mentioned in the note. I 

 have observed the same appearances with some of 

 the Coleopterous insects, where the development 

 occurs unmistakably in special cells. These par- 

 ticles are, according to my own observation, hair- 

 like with the Hirudinei, and Lumbricini, but are 

 pin-shaped with some of the Capitibranchiati. — Ed. 

 f [ § 164, note 1.] See also Leydig, Siebol (/and 

 Kolliker's Zeitsch. III. lift. 3, p. 318, and Quatre- 

 fages, Ann. d. Sc. Nat. XVI». 1852, p. 29» 

 {Branchellion). — Ed. 



