. 
176 THE ANNELIDES. $ 163. 
Spontaneous transverse fissuration occurs particularly with the Abran- 
chiati,® but has also been observed with the Nemertini,® and Branchiati. 
It occurs usually at the middle portion or at the border between the 
second and third segments of the body. Very often there may be per- 
ceived at this point, when this process has somewhat advanced, the place 
where, with the two future individuals, there will be a new fissuration. If 
the animal has a proboscis, tentacles, or eyes, these organs are developed 
with the posterior individual before its final separation. 
These animals have no trace of genital organs, while this process of divi- 
sion lasts. The individuals thus produced, re-divide, and this: division 
continues until a certain time of the year. It then ceases, and genital 
organs being developed, reproduction takes place by eggs. ; 
“The extreme vulnerability and reproductive power of many Chaetopo- 
des, give rise to their frequent multiplication by artificial and accidental 
division. The fragments thus produced are finally developed, and the mu- 
tilated animal ultimately regains its lost parts. Some have the power of 
voluntary division from the least handling of their body,® and these sep- 
arated parts are probably developed to new individuals. 
§ 163. 
Most of the Annelides reproduce by sexual organs, and the few Lumbri- 
cini which, as just observed, multiply by. fissuration, have probably, like their 
allied species, genital organs at certain seasons of the year.” 
The eggs of the Annelides present nothing remarkable; they are always 
spherical, and have a chorion and thin vitelline membrane containing a 
finely-granular vitellus with a germinative vesicle and dot. 
1 Lumbriculus, Nais, Chaetogaster and Aeolo- 
soma. 
2 See Johnston, in the Mag. of Zool. and Bot. I. 
1887, p. 534. 
8 With the Nereideae. 
4 Fissuration with many species of Nats, has 
already been noticed by O. F. Muller (Naturgesch. 
einiger Wurm-Arten des stissen und salzigen Was- 
sers. Taf. II. &c.), For that of Waits proboscidea 
and Chaetogaster diaphanus, see Gruithuisen, 
Nov. Act. Acad. Nat. Cur. XI. p. 248, Tab. XXXV, 
fig. 1,3; XIV. p. 412, Tab. XXV; fig. 2. For that 
of Aeolosoma, see Orsted in Kréyer’s Naturhist. 
Tidskrift. IV. Pl. IIL. fig. 7; and for that of Ne- 
reis prolifera, see Muller, Zool. Dan. IL. p. 16, 
Tab. LII. fig. 6. This last species isa very young 
Nereis. Itis probable that many other Branchi- 
ati multiply in the same way. Quatrefages (Fro- 
riep’s neue Not. No. 726, 1845, p. 344) has recently 
recognised a Syllis in Nereis prolifera. 
Sars (Faun. litt. &c. p. 87, Taf. X. fig. 18, 19) 
has observed multiplication by transverse division 
with Filograna implera, a young animal detach- 
ing itself from the caudal end of this Serpula. I have 
observed a like division with a Protu/a, a genus 
allied to Serpula. According to Milne Edwards 
(Ann. d. Sc. Nat. III. 1845, p. 180, Pl. XI.) a sin- 
* [§162, note 4.] See inthis connection, Schultze 
(Ueber, die Fortpflanzung durch Theilung bei Nais 
proboscidea, in Wiegmann’s Arch. 1850, p. 293). 
He has carefully described this form of multiplica- 
tion with this animal, and according to him it is a 
true fissuration, and not a gemmation, as that of 
Syllis, described by Frey and Leuckart. See fur- 
This 
gle individual of Myrianida fasciata, which is al- 
lied to Phyllodoce, produces six young by as many 
successively disposed divisions. According to Frey’ 
and Leuckart (Beitr. &c. p. 94, Taf. IL. fig. 1), 
there are with Syllis prolifera also, several young 
developed simultaneously, one after the other, at 
the caudal extremity.* 
5 See the experiments upon this subject with the- 
Lumbricini by Reaumur, Bonnet, Trembley, and 
Roesel. Dalyell (Froriep’s neue Not. No. 381, 
1840, p. 1) has observed a similar mode of repro- 
duction with Sabella. 
6 This has been observed by Grube, with Polia 
delineata (Zur Anat. d. Kiemenwiirmer, p. 68). 
Meckelia annulata has also the same property. 
1 Aeolasoma. 
2 See Wagner, Prod. Hist. gener. loc. cit. Tab. I. 
fig. 9,10 (Sanguisuga and Nephelis) ; Stannius, 
in Mudller’s Arch. 1840, Taf. IL. fig. 1,2 (Areni- 
cola piscatorum) ; Milne Edwards, Anu. d. Sc. 
Nat, III, 1845, Pl. V. fig. 2,3, Pl. IX. fig. 48, 44 
(Terebelia and Protula); and Sars, in Wieg- 
mann’s Aych. 1845, I. Taf. I. fig. 18 (Polynoé cir- 
rata). If the bodies which H. Meckel has figured 
(Miiller’s Arch. 1844, p. 481, Taf. XIII, fig. 13-. 
23) as the eggs of Lumbricus terrestris, are really 
such, which 1 think is doubtful, they differ much 
ther Leuckart, Ueber die ungeschlechtlichte Ver- 
mehrung bei Nais prohoscidea, in Wiegmann’s 
Arch. 1851, p. 184, Taf. II. fig. I-III. ; and Krohn, 
Ueber die Erscheinungen bei der Fortpflanzung vom 
Syllis prolifera und Autolytus prolifer. Ibid. 1862, 
p. 66. — Ep. : 
