214 



THE ACEPHALA. 



§196, 



remains to notice a very remarkable organ found in all the Lamellibranchia, 

 and known as the Gland of Bojanus. 



This organ, undoubtedly of a renal nature, is always double, and consists 

 of a large long sac with glandular walls, and of a dirty -yellow or dark- 

 green color. It is situated each side of the back between the pericardium 

 and the inferior adductor muscle, and extends usually upon the sides of 

 the abdomen to the base of the branchiae. 



Quite often these glands are united upon the median line of the back — 

 their cavities being separated only by a thin septum. They communicate 

 with the cavity of the mantle by two small openings which have swollen 

 borders and are situated sometimes at the upper, and sometimes at the lower 

 end of the sac.^-^ 



The usually very thin walls of these two sacs have numerous folds or 

 plicae, which form compartments or areolae, all of which are covered with, 

 a very delicate ciliated epithelium. The parenchyma of these walls is 

 composed of a very loose tissue, which, upon the least disturbance, sepa- 

 rates into small granular cells. ^'^^ Most of these cells contain a blue-black 

 round nucleus, to which is due the more or less deep color of these 

 organs."' 



(4) 



2 With Unio, and Anodonta, these orifices are 

 at the superior extremity of the renal sacs close 

 beside the two genital openings; see Bojanus, Isis, 

 1819, p. 46, Tat. I. fig. 1 ; Baer, in Midler's Arch. 

 1830, p. 319, Taf. VII. fig. 1, 2 ; Pfeiffer, Natur- 

 gesch. deutsch. Land-und Susswasser-Mollusken, 

 Abth. II. Taf. II. fig. 19, b. ; and Neuwyter, in 

 the Neue Denkschr. VI. p. 22, Taf. I. II. They 

 lie in the angle formed by the abdomen and the in- 

 ternal branchiae, and concealed beneath the inter- 

 nal leaf of these last. They had already been ob- 

 served by Poll (loc. cit. I. p. 6, Tab. IX. fig. 15, 

 i. i.), who, however, did not recognize their true 

 nature. 



With Pecten, and Spondylus, these renal sacs, 

 which are situated in front of the adductor muscle, 

 have their two orifices at the lower extremity ; see 

 Garner, Trans, of the Zool. Soc. loc. cit. Vl. XIX. 

 fig. 2,j. {Pecten). 



With many, the genital organs open into the 

 urinary ones. This is so according to Garner (loc. 

 cit. p. 92), with Tellina, Cardium, Mactra, Pho- 

 las, and Mya. I have very distinctly seen with 

 Pinna nobilis, the two orifices common to the kid- 

 neys and genital organs. Their borders were 

 swollen, and they were situated upon the anterior 

 surface of the dorsal wall a little in front of the 

 posterior adductor muscle. They opened into a 

 very large sac with thin walls which had no gland- 

 ular structure except at their lower extremity 

 near the principal adductor muscle ; see Poli, loc. 

 cit. Tab. XXXVII. tig. 2, D. 



The genital orifices open into the two sacs di- 

 rectly back of these external orifices. With Myti- 

 lus edulis, the kidneys have a yet more singular 

 arrangement ; their two sacs situated at the base 

 of the brauch iae are open their whole length, so 



that by spreading apart the branchiae, the com- 

 partments and cells of these glands can be distinct- 

 ly seen ; see Treviranus. Beobacht. aus d. Zool. u. 

 Phys. p. 51, fig. 68, b.* 



3 It is only recently that the intimate structure 

 of these organs was known, yeuwyler was quite 

 mistaken in regarding them as two testicles (loc. 

 cit. p. 25). He speaks of tubes in which he affirms 

 that he has seen spermatic particles, but he gives- 

 neither a detailed description nor a figure of one 

 or the other. I have never been able to find 

 anything of this kind in the Lamellibranchia. If 

 the walls of these organs are prepared in any way 

 for microscopic examination, a part of their paren- 

 chyma separates into a vesiculo-granular mass, 

 the particles of which have a very lively dancing 

 motion. The motions are due to portions of ciliated 

 epithelium adhering to the cells and granules. It 

 is in this way, probably, that Neuwy/er has been 

 deceived, taking these moving bodies for spermatic 

 particles. 



4 These round nuclei, usually of a deep brown or 

 blue color, can easily be seen in the kidneys of 

 Unio, Anodonta, and Cyclas ; but with the young 

 individuals their number and size are quite lunited, 

 making the kidneys very pale. • They resemble, 

 moreover, perfectly the bodies contained in the 

 renal substance of the Gasteropoda (see below). 

 This analogy is particularly striking with Asper- 

 gillum vaginiferum, whose renal sacs are tri- 

 angular and situated between the heart and the 

 extremity of the rectum, thus resembling in all re- 

 spects the kidneys of the Gasteropoda, although 

 Leuckart has taken them for the liver (Neue, wir- 

 bellose Thiere d. roth. Meeres, loc. cit. p. 46, Taf. 

 XII. fig. 6, g.). 



alone. This would seem inefficient did we not re- * I § 196, note 2.] According to Frey and 

 member their unceasing action ; and this view is Leuckart, the bodies of Bojanus are absent in 

 the only one which will explain the exact conform- Teredo navalis, but these observers think the kid- 

 ation of the excavation to the shape of the body in ueys are present in another part of the body j see 

 all its parts. It is the view of Agassiz, and others, loc. cit. p. 46. — Ed. 

 who have si)eciaUy examined the subject. I have 

 here thus noticed the matter in a suggestive poiut of 

 view for microscupi'jal anatomists. — Ed. 



