394 NOTES AND MEMORANDA, 
little light-loving Entomostraca. Any artificial light, even 
a common candle, is to be preferred to sunlight, for the former 
and your tank are relatively fixed ; besides, sunlight,-however 
desirable, is not to be got in the cabins or wardroom of a 
man-of-war, and naval etiquette interdicts a seat, much less 
a microscope on deck. When properly illuminated there is 
no difficulty in picking out the larger objects with a dip-tube 
and dropping them into a suitable cell. But all this 
occasions the third and fourth disturbances of the water, and, 
if an Appendicularia is captured enclosed in his “ haus,” he 
is perfectly certain to be frightened out of it before he gets 
under the microscope. ‘To avoid the last disturbance I have 
made a dip-tube with thin parallel sides which could be 
used as a slide or cell. My first attempts were too large, 
and the water ran out when the tube was placed horizontally 
across the stage of the microscope, but I finally succeeded 
in producing a tube which works fairly well. 
The more minute creatures along with the hosts that are 
invisible to the naked eye, excepting as a whiteness in the 
track of the ray, are best collected for observation by a 
small-bore siphon, with a shred of cotton wool in the short 
arm. 
The water should pass through by drops, and the filtrate 
will after a time be almost perfectly clear. It does not 
remain so, however, for after some hours it becomes faintly 
cloudy, though I cannot detect the cause with the microscope. 
The filtrate is very useful to keep one or two specimens in 
if there is anything about them in a transitional state. I 
have thus watched part, but unfortunately not all, of the 
development of the groups of spermatozoids sometimes met 
with on Noctiluca. 
The cotton wool first entangles Chetoceros and any united 
diatoms, and soon becomes completely plugged, at least in 
the Pacific waters, with Peridinia, young Polycystina, and 
Foraminifera, together with many other forms that I cannot 
even class without books of reference—Epwarp L. Moss, 
M.D., F.R.C.S.1., Royal Naval Hospital, Esquimalt, Van- 
couver’s Island. 
Spermatozoa of Petromyzon.—Mr. George Gulliver, F.R.S..,! 
communicates the following note to the Proceedings of 
the Zoological Society of London, April 20th, 1875. 
In my paper “On certain Points in the Anatomy and 
Economy of the Lampreys,” published in 1870 (P. Z. S. 
1870, p. 844), there is an engraving of the spermatozoa of 
Petromyzon planert. But I know not that those of P. marinus 
