276 
NOTES AND MEMORANDA. 
Tornaria is the young condition of Balanoglossus . — Professor A. 
Agassiz, writing to the ‘American Naturalist,’ for November, states 
that the “ development of Tornaria bas at last been solved. As is well- 
known, Muller, Krohn, Fitz Muller, and myself have considered it a 
star-fish embryo. The analogy between a Brachiolaria and Tornaria 
seems complete, and no one questioned the position of the latter till 
Metznikoff in 1870 was fortunate enough to raise Tornaria to a later 
phase of development — to his astonishment it changed into an annelid. 
Of course, in view of the affinities (first suggested by Huxley) of the 
worms and echinoderms, it was most important that Metznikoff’s 
observations should be repeated, and if possible the genus of annelids, 
of which Tornaria was the young, accurately ascertained. The 
annelid raised by Metznikoff was most peculiar, and, in absence of 
other evidence, he suggested the possibility of its being a young 
Balanoglossus. I have been able this summer to raise Tornaria and 
to obtain young annelids somewhat older than those observed by 
Metznikoff, tracing at the same time the development of the branchiae 
as diverticula from the oesophagus, and also to find the young annelid 
of Tornaria a species of Balanoglossus (of which the adult is quite 
common at low-water mark at Newport and at Beverly, Mass.), but 
slightly older than those raised directly from the Tornaria stage. 
The details of this interesting embryology will shortly be published.” 
NOTES AND MEMORANDA. 
How to Measure Angular Aperture— The following plan, whose 
novelty is almost questionable, is given in a recent number of the 
‘ American Naturalist — For those students whose stands have not a 
graduated rotating base, Professor T. D. Biscoe recommends a plan 
especially applicable to the larger form of achromatic condensers 
which cannot be as conveniently arranged for the method advised by 
Dr. Carpenter. He places the combination horizontally, with a gas 
flame several feet distant behind it to furnish nearly parallel light, 
holds a card across the centre of the front lens so as to bisect the 
cone of light, and with a fine pencil marks the edges of the illumi- 
nated portion of the card. A common protractor is used to measure 
the angle of the lines thus drawn. Though chiefly useful to 
measure the eye-piece form of achromatic condensers (Webster’s 
condensers, &c.) as actually used with diaphragm, &c., in position, the 
method may be sometimes convenient for objectives of low power. 
Professor Biscoe believes it can be applied to objectives as high as 
] inch of 110° and be reliable within one or two degrees. 
A New Erecting Prism— The ‘Journal of the Franklin Institute ’ 
(U.S.A.) states that Mr. Joseph Zentmayer exhibited at a meeting of 
the Franklin Institute a single prism which erects the image com- 
