308 SUMMARY OF CURRENT RESEARCHES RELATING TO 
nutritive influence is restricted to the period stated. We venture to 
hope tliat in tlie continuation of this excellent work the author will 
expound his conclusions more methodically. 
Cyclic Reproduction in Rotifers.* — According to Dr. R. Lauter- 
born’s observations extending over a period of six years, there exhts in 
the pelagic Rotifers a periodicity in the production of males and fecun- 
dated resting eggs. These are produced at certain times of the year, 
which times do not always correspond with the beginning of the cold 
season. A certain number of Rotifers are perennial. Others appear 
only during the summer months, and these produce males only once a 
year (monocyclic), generally from the end of August to the end of 
October, at the end of a long series of parthenogenetic generations. 
After this period they gradually disappear completely ; but they appear 
again the following spring or summer. In the perennial Rotifers, 
which can be found more or less abundantly all the year round, there 
are two or more sexual periods in the year during which males and 
resting eggs are produced (dicyclic and polycyclic). In the Rotifers 
which have two sexual periods, such as Asplanchna priodonta , the first 
occurs in the spring (particularly April), and the second in the autumn 
(September and October) ; whilst during the winter and middle of sum- 
mer such forms produce no males or resting eggs. The polycyclic 
forms have more than two sexual periods, cr may produce males all the 
year round. 
From these observations the author draws the conclusion that the 
beginning of the sexual period in Rotifers is not caused primarily by 
external circumstances, such as heat, drought, or want of food, according 
to the accepted belief, but that it is due in the first instance to the mode 
of development of each species, which may however become modified by 
the influence of such external circumstances. 
The author further confirms, in the case of Asplanchna prioclonta , 
whatM. Maupas had previously observed in Hydatina , namely that some 
females of A. priodonta produce parthenogenetic summer eggs and others 
parthenogenetic male eggs, and that these male eggs alone become changed 
into resting eggs if they are fertilised. In Asplanchna, of course, the 
summer and male eggs are not laid, but develop in the uterus. Th<f 
author observed the sjDermatozoon which had entered the resting egg in 
process of formation, its transformation into the male pronucleus, and 
the conjugation of the two pronuclei. 
Rotatoria of New Guinea. | — Dr. Daday has examined some spirit- 
material collected by Dr. L. Biro in New Guinea, and found therein 47 
species of Rotifers, ten of which are described as new, with his usual 
disregard of already hnown forms. At least three of the new species 
are “ old friends,” while four or five more are quite unrecognisable 
and therefore “ dead,” leaving only two that can properly be called 
new. The alleged new species are the following : — Asplanchna papu- 
ana (described from the jaws only, which may very well be those of 
A. myrnieleo ), Megalotrocha hinotata (= M. semibullata Thorpe), Diplax 
ornata ( = Distyla ludwigii Eckstein), JBrachionus papuanus ( = var. 
* Biol Centralbl., v. (1898) pp. 173-83. 
f Mathem. Termesz. Ertesito. Budapest, 1897, pp. 131-18 (9 figs.). 
