NOTES AND MEMORANDA. 37 



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." 



'f^j.. " In the yellowish, or, as we may for convenience call it, the me- 

 dullary 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 coloiirless." 



" 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 circulation, 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 

 homologue in the lower orders of Crustacea, which is suj)posed 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 re2)resents the glandular portion of the segmental organs in 

 worms. That so large and important 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 caj)sule of 

 the vertebrates, analogues of which are said by Leydig to exist in 

 Paludina and Pontobdella." 



" Eeasoning from their histological structure, and by exclusion, it 

 seems not imi^robable 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 Ehizocephala, and said by him to be ' situated on each 

 side of the middle jiart of the animal, and generally coloured yellow 

 or red (primitive kidneys ?).' * " 



" I may add that all these observations were made on living 

 Limulus Polyphemus, in the laboratory of the Anderson School of 

 Natural History at Penikese Island, Mass." 



NOTES AND MEMORANDA. 



Browning's Platyscopic Lens.— Mr. J. Browning has recently 

 produced a form of pocket lens, which he has called the platyscopic, 

 and which certainly for extreme flatness of field is superior to the 

 Codrington or any other lens that we have seen. We have given it 

 careful trial ere expressing our opinion, and we consider that while 

 lower in power it possesses advantages which make it, jmr excellence, 

 the first in the field. It is a triple achromatic combination, in which 

 * 'Annals and Mag. N. H.,' Nov. 1874, p. 383. 



