Crystals in the Intestines of Artemia Salina. 95 



with the naked eye, or "with a low power, the branchial feet are 

 constantly waving like graceful plumes, and they carry their 

 owner now up, now down, now this way, now that, the move- 

 ments being rapid, elegant, and under perfect control. In the 

 females, which are most common, alarge squarish pouch, situated 

 under the first joint of the abdomen, carries numerous round 

 dark eggs, and forms a conspicuous object whichever way the 

 Artemia is viewed. 



As is common with entomostracans, the young brine shrimps 

 differ considerably from their parents, but with successive 

 moul tings acquire the same form. The gill feet are exquisite 

 objects for the microscope, and powers of 500 to 1000 linear 

 reveal a multiplicity of structures, amongst which vessels bulg- 

 ing in the middle, and tapering towards a duct at each end, are 

 very noticeable. The incessant motion is essential to respira- 

 tion, by bringing fresh currents of water into contact with the 

 delicate membranes of which the gills are composed, and it is 

 also subservient to purposes of locomotion. If a female, with 

 her external ovary filled with eggs, is thrown into fresh water, 

 she survives some time, but, though the gill feet labour as hard 

 as before, she fails to swim, being too heavy for the lighter 

 medium. When replaced in her favourite brine, the swimming 

 proceeds as vigorously as ever, and no harm appears to result 

 from a temporary immersion in the fresh fluid. 



It was about the middle of June that, through the kindness 

 of Mr. Burr, I received my first batch of these pretty creatures, 

 and on the 20th I noticed in the intestines of some, beautiful 

 groups of crystals, composed of prisms arranged in aigrettes, 

 very much like the figures of uric acid in Micrographic Dic- 

 tionary, plate 8, fig. 1 1, and exactly resembling the larger forms 

 depicted in Dr. Glover's Manual of Chemistry, plate 11, fig. 47 b. 

 Every specimen of this batch, which I subsequently examined, 

 contained crystals of the same form in more or less abundance, 

 and one was crammed with them, a single mass composed of 

 many coalescing groups, measuring 22 — 1000'' in its longest 

 diameter. With the polariscope they presented a beautiful 

 appearance, and this fact, together with their virtual insolubility 

 in water, confirmed the impression that they were composed of 

 uric acid, a substance well-known to exist in the secretions of 

 Crustacea ; but not, so far as I am aware, previously noticed as 

 forming calculi in any entomostracan. 



On the 4th July Mr. Burr obligingly gave me another supply 

 of specimens, brought a few days before from Hayling Island. 

 These were in a much more delicate state than the preceding. 

 None were healthy, and many were dead, with oddly stiffened 

 tails. My mode of examining these, as in the former case, was 

 to cut off the abdomen, place it in a drop of clean fresh water, 



