20 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
ordinarily finely filamentar delicate and clear protoplasm, in which about 
four nodal points may stain ; it passes into a triangular tip which con- 
tains a slightly colourable corpuscle, and has the appearance of a recurved 
hook. Without staining or the use of immersion lenses only the tip and 
not the shaft of this “ spear ” is visible. At the base of the “ spear ” 
there is a corpuscle of elongated form. 
The head is succeeded by a quite short, clear neck, in which a rounded 
corpuscle may often be seen, and this by a mid- or connecting piece. 
The “ protoplasmic remains ” which cover the neck vary in size with the 
age of the spermatozoon. The boundary between the mid-piece and the 
tail is always to be seen as a dark line. The whole of the mid-piece and 
of the tail, with the exception of Betzius’s terminal piece, is surrounded 
by a protoplasmic fringe, which has a spiral course. 
The form of the human spermatozoon is not always the same, and 
in the fresh state Prof. Bardeleben has observed five or six varieties ; 
some are gigantic, being about 7‘5 /j. long and 3 '75 fi broad. 
There are various forms of movement, and the head itself may 
undergo changes in form. Within it there go on movements which 
indicate processes of division, and lead to the ejection of part from the 
head. In other words, polar bodies are formed just as in the ovum. 
This remarkable discovery explains the presence of the number of small 
bodies which have often been observed in sperm. 
In the spermatozoa of all animals we must distinguish (1) generative 
matter, (2) nutrient matter (protoplasm or yolk), (3) motor protoplasm, 
(4) arrangements for entrance into the egg. The first of these is found 
in the head ; the second, which is comparable to the nutrient yolk of the 
egg, is found in the protoplasmic remains on the neck, which become 
gradually absorbed in the head-cap, &c. The forward movements are 
effected by the tail, which can function as a fin as well as a screw. The 
arrangements for entrance into the egg consist of a spear, which may be 
produced into a recurved hook, and in the sjnral fringe of the tail, 
which allows of boring movements. 
The author is unable to decide whether spermatozoa make use of any 
foreign protoplasm or replace it by symbiosis with leucocytes. It is 
quite clear that the spermatozoon is a true cell, which differs from the 
ovum in its power of active movement. 
y. General. 
Primitive Movements of Animals.* — Prof. J. Frenzel points out 
that a Flagellate, e. g. Euglena, may swim without moving its flagellum, 
or even without one, that the Heliozoa swim without any visible change 
in their rays and without rotation, that the same is true of the protist 
Nuclearella, and that Gregarines also move without changing their 
shape. So diatoms move without, Frenzel says, visible locomotor struc- 
tures, and may attract small lifeless particles towards them. The same 
power of movement without locomotor structures is seen in some bacilli, 
and minute cocci are well known to exhibit a so-called “ Brownian 
movement.” 
Some spermatozoa, e. g. those of the cockroach, move in definite 
orbits, as has been shown by Eimer and Dewitz ; the spermatozoa of 
* Biol. Centralbl., xi. (1891) pp. 464-74. 
