Observations on British Zoophytes and Protozoa, 271 
state of the sarcode as occurring in spirit specimens of Orhi- 
tolite, which appeared to be broken up into little spherules, 
though still retaining the structure of unchanged sarcode. 
He also states that similar spherules are figured by Ehren- 
berg in several of the cells of Sorites orhiculits, and by 
Schultze in the chambers of Botalia. Dr Carpenter is in- 
clined to believe that these bodies are gemmules. I have 
repeatedly noticed bodies, apparently similar to those figured 
by Carpenter, in Gromia ; but I have considered them to be 
of the same nature as the coloured spherules which are found 
within the endoderm of the Hydroid Zoophytes. 
Besides these spherules, however, Dr Carpenter has met 
with other bodies, apparently imbedded in the sarcode, which 
he considered might be gemmules in a later stage, or ova. 
These were of a deep-red colour, and exhibited various 
stages of binary division. He has also figured a third ob- 
ject, found in an imperfectly closed shell of OrhitoUte, which, 
with his usual caution, he considered might possibly have 
been introduced from without. 
It is under these circumstances that I bring forward the 
following observations. 
With regard to the female element, it will be necessary 
first to ascertain the essential characters of an ovum. Pro- 
fessor Allan Thomson* defines it as "a detached spheroidal 
mass of organised substance, of variable size, enclosed in a 
vesicular membrane, and containing, in the earlier periods 
of its existence, an internal cell or nucleus." But the pre- 
sence of a nucleus is not essential to the constitution of an 
ovum ; for in the ova of Chrysaora hyoscella and some of the 
Ctenophora (Beroe) it cannot be detected at any stage. 
The ova of these animals may be defined as " detached 
masses of highly refractive substance." Such appears to be 
the simplest definition of an ovum — a definition which will 
apply also to the first stage of the ovum of Bhizostoma as 
figured by Professor Thomson,t where he shows, first, the 
primitive ovum" destitute of germinal vesicle and spot ; 
secondly, the appearance of the germinal vesicle ; thirdly, 
* Cyclopaedia of Anat. and Pbys., vol. v. p. 128. 
t Op. at. p. 128. 
