§ 293. THE CRUSTACEA. 80F 
which, with the Idotheoidae, and Asellina, are two pairs of similar seminal 
tubes. The two Vasa deferentia converge towards the posterior portion of 
the body, where they pass into a double, or a single excretory canal; which 
usually commences directly in front of the first pair of post-abdominal feet, 
on the median line of the body.“ With the Isopoda, this excretory canal 
opens into a short, backwardly-curved penis, upon which are two long 
processes (secondary penises) inserted on the internal border of the second 
pair of feet.“ 
With the Stomapoda, the testicles consist of more or less ramified, gland- 
ular lobes, from which pass off, laterally, two Vasa deferentia which ter- 
minate in two hollow penises projecting at the base of the last pair of 
feet. 
With the Brachyura, and the short-tailed Anomura, the two testicles 
consist of a net-work of very small semeniferous canals, occupying the lat- 
eral portions of the cephalothorax, which gradually increase in size until 
they pass into the long Vasa deferentia. These last form numerous convo- 
lutions, and are finally continuous into two larger Ductus ejaculatorit.“? 
With the male Paguridae, the testicles are contained, like the ovaries, in 
the tail. They consist of two large tubes which rapidly contract into a Vas 
deferens, which is straight,-at first, but afterwards spiral. This then 
becomes larger and is gradually continuous into a Ductus ejaculatorius.™ 
With some Macrura, the cephalothorax contains two anterior and two 
posterior testicular tubes, a portion of the last being’ extended even into 
the tail; while the first are connected, by a transverse anastomosis, behind 
the middle of the body. The two posterior join with the two anterior in 
the posterior extremity of the cephalothorax, and form on each side, a short, 
narrow, deferent canal, which terminates in a larger Ductus ejaculatorius. 
18 With Cyamus, whose caudal extremity is 
atrophied, the orifices of the two excretory ducts 
are situated directly in front of the arms on two, 
side by side papilliform penises (Roussel de 
Vauzeme, hoc. cit. p. 252, Pl. VIII. fig. 7, 15). 
With Aega, the two testicular tubes are curved S- 
like on the sides of the cesophagus. Their defer- 
ent canals are dilated at the posterior extremity 
each into a seminal vesicle of the same S-like form. 
They open through two approximated papillae 
situated on the under surface of the last foot-bear- 
ing abdominal segment (Rathké, Nov. Act. Nat. 
Cur. XX. p. 32, Tab. VI. fig. 16). 
The three testicles which are found on each side 
of the thorax with Idothea, Lygia, Lygidium, 
Asellus, Porceilio, Oniscus, &c., are very atten- 
uated in front, but behind, are enlarged into a kind 
of bulb before passing into the Vas deferens. 
Cavolini (loc. cit. p. 155) has already carefully de- 
scribed these with Lygia oceanica. See, more- 
over, Milne Edwards, Hist.d. Crust. Pl. XII. fig. 
13 (Lygia); Brandt, Mediz. Zool. II. p. 76, Taf. 
XV. fig. 31 (Oniscus), and Lereboullet, loc. cit. 
p. 132, Pl. V. fig. 1384 (Lygidium). 
14 The copulatory organs of the Asellina have 
been described and figured by Brandt (loc. cit. p. 
73 and Taf. XV. fig. N.V. Z.). Treviranus, also 
(Verm. Schrift. I. p. 59, 74, Taf. VIII. fig. 48, 49, 
Taf. XII. fig. 65-67), has well represented them 
with Porcellio, and Asellus, although he entirely 
overlooked the six testicles of these Crustacea. 
The penis, and its auxiliary stalks, which, with the 
Isopoda are always concealed in the midst of the 
branchial lamellae, have been figured by Degeer 
(Abhandl. zur Geschichte d. Insekt. VII. p. 191, Taf. 
XXXII. fig. 6, 20), and by Rathke (loc. cit. p. 128, 
Taf. IV. fig. 16,17, f. h. 25) with Idothea ento- 
mon ; but this last author is quite mistaken about 
the internal genital organs, having confounded 
the male with the female (loc. cit. p. 123, fig. 22). 
Ihave already corrected this’ error in Miller’s 
Arch. 1837, p. 434. Savigny, also (Descript. de 
V'Kgypte, Crust. Pl. XII. XIII.), has given beauti- 
ful figures of the copulatory organs of Sphaeroma, 
Lygia, Idothea, Tylos, and Oniscus. The 
secondary or auxiliary penises have been repre- 
sented by Lereboullet, loc. cit. p. 120, Pl. V. fig. 
19 (Lygidium), and by Milne Edwards, Arch. du 
Mus. IT. p. 21, Pl. Il. fig. 3.* b.1. (Serolis), and 
Ann. d. Sc. Nat. XV. 1841, Pl. VI. fig. 4 (Lygia). 
15 As to both form and position, the multilobular 
testicles of Squilla almost exactly resemble“the 
ovaries. But their lateral lobes are not blended 
together at the anterior extremity of the body, and 
the two deferent canals are given off laterally 
(Delle Chiaje, Descriz. &c. Tav. LXXXVI. fig. 
4). The two penises of these Crustacea have been 
correctly figured in Desmaret’s Considérat. &c. 
Pl. XLIL. n. 0. 
For the male organs of Mysis, of which the tes- 
ticles are composed of only a few lobes, see Frey, 
loc. cit. p. 26. 
16 Cavolini, loc. cit. p. 144, and Milne Ea- 
wards, Hist. d. Crust. I. p. 166, and Cyclop, loc. 
cit. p. 783, fig. 418 (Cancer pagurus). 
li Swammerdamm, loc. cit. p. 86, Taf. XT. fig. 6, 
and. Delle Chiaje, Descriz. &c. Tay. LXXXVI. 
ig. 6. 
18 Milne Edwards, Hist. d. Crust. Pl. XII. fig. 
15 (Homarus), and Delle Chiaje, loc. cit. Tav. 
LXXXVII. fig. 6 (Scyllarus). 
