undescribed Organ in Limulus. 257 
form, and, twenty hours after the portion of the parenchyma 
submitted to microscopic examination, vibrated to and fro. 
I am reminded in the vibrating movements of these bodies 
of Siebold’s description (‘Anatomy of the Invertebrates ’) of 
similar bodies in the renal organs of the Lamellibranchs, 
7. e. the gland of Bojanus. He says in a footnote, p. 214 
(Burnett’s translation) :—“ If the walls of these organs are 
prepared in any way for microscopic examination, a part of 
their parenchyma 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.” 
In other portions of the outer reddish part of the gland, 
where the pigment(?) masses are wanting, the mass is made 
up of fine granular cells, not nucleated. Other cells have a 
large nucleus filled with granules and containing nucleoli. 
In the yellowish or, as we may for convenience call it, the 
medullary portion are scattered about very sparingly what are 
probably the round secreting cells. The nucleus is very large 
and amber-coloured, with a clear nucleolus; others have no 
nucleolus ; and the small ones are colourless. 
I am at a loss to think what this gland, with its active 
secreting cells filled with a yellowish fluid, can be, unless it 
is renal in its nature. This view is borne out by the fact 
of its relation with the hepatic and great collective vein. If 
future examination shows some outlet into the venous circu- 
lation, then its renal nature would seem most probable. No 
other organ that can be renal in its nature exists in Limulus. 
In its general position and relations it is probably homologous 
with the green gland of the Decapod Crustacea and its homo- 
logue in the lower orders of Crustacea, which is supposed also 
to be renal in its nature. It may also possibly represent the 
organ of Bojanus in the Mollusca, which is said to be renal 
in its function. It perhaps represents the glandular portion 
of the segmental organs in worms. That so large and im- 
portant a gland is an embryonic gland, in adult life aborted 
and disused, is not probable; nor is there any good reason for 
regarding it as analogous to the suprarenal capsule of the 
vertebrates, analogues of which are said by Leydig to exist in 
Paludina and Pontobdella. 
Reasoning from their histological structure and by exclu- 
sion, it seems not improbable that these glands are renal in 
their nature, and homologous with the green glands of the 
normal Crustacea. They seem also homologous with the 
organs described by M. A. Giard in the Rhizocephala, and 
