ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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Clavellina ; ( b ) by incipient reduction as in (a), but followed by total 
resorption into the stolon, which may grow during the process. Resorp- 
tion is due to the migration of. the individual cells out of the tissues 
into the haemocoel. In certain conditions the zooid maintains itself, in 
spite of food not being provided, at its original size and in perfect 
health. This it does by resorbing the stolon. This happens in slightly 
unfavourable conditions, which affect the sensitive zooid more than the 
less highly organized stolon. The stolon tends to be starved at the 
expense of the zooid. The zooid is more susceptible to toxic agencies. 
In low concentrations of toxic agencies it is therefore affected, while 
the stolon is not. As a result it begins to de-differentiate, and cells 
migrate out of the tissues. The speed of the zooid’s metabolic pro- 
cesses is no longer greater than that of the stolon’s. It is therefore 
starved at the expense of the stolon. Any cells migrating out of the 
tissues are removed by the normal circulation, by the stolon-circulation 
(irregular pulsation of the stolon), or by utilization as food by the 
stolon. As in chemical reactions where the end-products are removed, 
the reaction thus runs to its limit, i.e. to complete resorption of the zooid. 
Stopping the circulation by KC1 lessens the degree of resorption. At 
low temperatures (about 5° C.) there is some de-differentiation, but very 
little resorption. The general biological aspects of de-differentiation 
are discussed. J. A. T. 
O 
New Styelid Tunicate from Norway. — Augusta Arnback- 
Christie -Linde ( Bergens Mus. Aarbok ., 1921, 20, No. 3, 1-8, 1 ph). 
A description of Styela theeli sp. n., from Hardanger. It agrees in some 
external and internal features with the members of the group Goniocarpa , 
but it has two gonads on one side and one gonad on the other, whereas 
in the Goniocarpa group there is one on each side. In the canopus 
group there are two on each side, so that 8. theeli is in this respect 
intermediate. The single specimen was dredged along with 8. loveni 
and 8. rustica, but it seems to be quite distinct from any known species 
of the genus. J. A. T. 
Parallelism in Ascidians. — A. G. Huntsman {Proc. Amer. Soc. 
Zool. in Anat. Record , 1922, 23, 92-3). Ascidians in general and 
Styelidse in particular offer very good illustration of parallelism in the j 
evolution of body-form. In Styelidae. the outstanding fact is the 
repeated appearance of a peculiar stalked type in distinct genera. It is 
suggested that the lines are limited, not by selection, but by the struc- 
ture of the ancestral germ -plasm. There are internal architectonic 
conditions depending ultimately on the structure of the living matter. 
J. A. T. 
INVERTEBRATA. 
Mollusca. 
7. Gastropoda. 
Effect of Ultra-violet Rays on Developing Limnaeus. — C. W. M. 
Poynter ( Proc . Amer. Ass. Anat. in Anat. Record , 1922, 23, 32-3). 
Lethal and monstrous effects are readily produced, but embryos are 
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