STRETHILL WRIGHT, ON BRITISH ZOOPHYTES. 4H 
thus as readily and perfectly illustrated as by any other pro- 
ceeding hitherto promulgated. 
Measurement of the cells—The utmost variety exists in 
the magnitude and form of these bodies ; they are usually de- 
scribed as globular in man, and Car penter assigns them a 
diameter of from —a5;th to ith of an inch. 
Kolhker gives a diameter of from ‘05’ to 06" for the larger 
variety, which, being reduced to fractional parts of the Eng- 
lish inch, shows a range of from ;1,th to ;1,th of an inch. 
My own measures of the cells in the ox, which, though for 
the most part are of a peculiar elongated form, are some of 
them more globular, average— 
In length, from zooth to rsoth of an inch. 
In br eadth 9 46 voth 270 Seo voth 9 
Nucleus 3) TOT ie ith > T00 a 0 =th 3) 
Nucleolus _,, Sas TD ppeetai 
Kolliker gives to ine oe in man a diameter of 0:0015”” 
to :008’”, or from 73,7 to +,15,th of an Bugs inch, hee to 
the nucleolus one of 0:0005’” to 003" for" th to 2. th 
of an English inch. 
In ~,th of an inch square, or the =1,th part of a square 
inch, I have counted forty-nine large, elongated cells ; whence 
it may be estimated that there are between three and four 
hundred thousand nerve-cells in a cubic inch of the cineri- 
tious substance in the spinal cord of the ox. How vast, 
therefore, must be their number computed throughout the 
entire length of the cord; how complex their relations, and 
how marvellous their functions, whether we regard them as 
active centres of growth and reparation, or the source them- 
selves of nervous power. 
ee 3) 
OxBsERVATIONS 02 British Zoopuytges. By T. StretHiyy 
Wrieut, M.D., F.R.C.P. Edin. 
1. On Reproduction in Aquorea vitrina. Communicated to 
the Royal Physical Society of Edinburgh, November 27th, 
1861. (Pl. IV). 
In vol. i of Agassiz’s ‘Natural History of the United 
States’ the following passage occurs:—“ As to the A‘quo- 
readz, I have no doubt that they are genuine Hydroids, though 
I have not been able to trace with certainty the origin of the 
