SCIENTIFIC SUMMARY. 
285 
MICROSCOPE. 
Supposed Discovery of a Microscopic Vertebrate Jaw. ■ — Dr. Wallich 
figured the “ Annals,” a minute object which he had found upon a slide 
containing mud, dredged off St. Helena. It was about the -rcnrth of an inch 
in length, and bore so remarkable a resemblance (as the writer can vouch 
from personal examination of it) to the lower jaw of some mammalian 
animal, that it has been a puzzle to naturalists, who have referred it — some 
to the mandible of a fish ; others to the lingual ribbon of a mitra ; others to 
the claw of a minute crustacean ; and others yet again to the valve of a 
pedicellaria (or minute process found upon sea-urchins). After due con- 
sideration, no one now believes that it ever formed part of a vertebrate 
animal ; but its interest as a pseudomorph (or imitator of another natural 
form) is undiminished. Mr. Spence Bate makes out a good case for its 
being the last joint of the leg of a small hyperine crustacean, of the genus 
Phrosina, which is very abundant in the tropical and subtropical Atlantic 
Ocean. Dr. Wallich himself inclines to favour the opinion of Mr. Busk, 
who shows the extremely close analogy between the object in question and 
certain Pedicellarise. 
Presence ofAcari in Solutions. — The circumstance mentioned in the last 
number has received elucidation from a paper by Mr. Shadbolt to the 
Microscopical Society. The Acari found in these unusual situations 
appear to belong to a widely diffused species, which has been found 
adhering to the walls of a room in great numbers, whence they make their 
way into the solutions. The remarkable fact still remains, however, of 
their being found in strong nitrate of silver baths, which might be expected 
to be fatal to animal life. It is probable that the Acarus Crossii, at one 
time supposed to have been produced by the electrical experiments of 
Messrs. Crosse and Weeks, was of the same species. 
Urticating Filaments in Mollusca. — Dr. Bergh, of Copenhagen, has shown 
that these minute organs exist not only in Hydra, the Actiniae, and the 
Medusae, but also in several Molluscs. He has demonstrated the existence 
of true urticating batteries of sacs filled with cnida (or nettling filaments) 
in the typical forms of Eolidrn, and in several other genera of naked-gilled 
Mollusca. They may be almost regarded as a family character. In every 
case they are planted at the extremities of the papillae, above the hepatic 
lobe, in a sac opening to the exterior by an extremely minute pore at its 
summit. Although called urticating filaments, it is probable that they 
have not a true urticating function ; for stinging is not always a conco- 
mitant of their presence, as in the case of these Eolids. The use of them 
must, therefore, be regarded as at present unknown. 
New Method of preparing Algce, <&c. — Professor Reinicke recommends 
the following mixture as a dense, non-drying fluid, which prevents the 
shrinking of soft tissues; viz. alcohol (90°), 8 parts; water, 2 parts; 
glycerine, 1 part. The spirit, being lighter and more limpid than water, 
compensates for the greater density of the glycerine. The preparation 
