3S2 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
In a criticism of observations on regeneration in hermit-crabs by 
Morgan,* * * § Prof. Weismann somewhat modifies the statements just made* 
by admitting that the regeneration of the abdominal appendages in the 
hermit-crabs does not prove that these appendages are now liable to injury, 
but merely that they formerly were so liable, or that their power of 
regeneration may be an inheritance from the worm-like ancestor of the 
Crustacea, which had doubtless a well-developed diffuse power of re- 
generation. 
The fact that in some cases in Insects and Crustacea the appendages' 
which are regenerated are of an older type than those lost, shows, accord- 
ing to Prof. Weismann, that the power of regeneration depends upon the 
existence of regeneration primordia. After some further discussion of 
these primordia, Prof. Weismann passes to the general discussion of his 
theory of heredity. In the course of this he reaffirms his belief in the 
occurrence of “ reducing-di visions ” in the maturation of both male and 
female germ-cells, and defends himself against those who object to the 
want of stability in his views. 
Regeneration in Crustacea.f — Herr Hans Przibram has made a pro- 
longed series of observations on this subject in the fresh-water Ento- 
mostraca. He also summarises the observations of others on other 
Crustacea, and gives a table illustrative of the distribution of regene- 
rative power in the animal kingdom. His conclusion is that the power 
of regeneration is primitive, and tends to disappear as specialisation 
advances. Further, in accordance with “the fundamental biogenetic 
law,” the individual tends to recapitulate its race-history, and therefore 
the power of regeneration is greatest in early life, and gradually 
diminishes during the course of the life-history. 
Variations in the Plankton of Lake Geneva Prof. Emile Yung 
estimated these every fifteen days or so during 1898, and has reached the 
following conclusions : — 
(1) The distribution is in no way homogeneous ; it varies from place 
to place, both horizontally and vertically, chiefly through the formation 
of swarms. 
(2) The plankton extends to 200 metres, even below the “ light- 
limit.” Abundant Cladocera ( Dajplinia and Sida :) were got from 150— 
200 metres. 
(3) The quantitative maximum is in May and June, when the water 
had a superficial temperature of 13°— 14°. The minimum is in March 
and September, but there seems to be an autumnal maximum in Novem- 
ber or December. 
(4) Apstein’s net w r as used, but its defects are great ; so great that 
the results cannot be said to have more than relative value. Hensen’s 
coefficient of filtration, intended to correct errors, is illusory in a lake 
where the composition of the plankton varies from month to month. 
Lake and Pond.§ — Dr. O. Zacharias has inquired into the difference 
between a lake and a pond. The criterion is usually found in depth. 
* Zoo], Bull. Boston, i. (1898). 
t Arbeit. Zool. Inst. Univ. Wien, xi. (1899) pp. 163-94 (4 pis.). 
t Tomptes Kendus, cxxviii. (1899) pp. 1128-30. 
§ Biol. Centralbl.. xix. (1899) pp. 313-9. 
