616 Marvels of the Universe 
microscope it is interesting to watch the circulation 
of its blood; this is quite transparent, and contains 
small round globules, which traverse the stream in 
pulsations every second. Little is known of its 
means of respiration, but it is supposed that the 
constant motion of the swimming-feet previously 
referred to is associated with the function. On the 
other hand, the curious two-lobed tail-plate, as it is 
called, has been thought to be an organ of respira- 
tion, but its primary use is no doubt as a rudder. 
In the female Argulus, previous to the deposit- 
ing of her eggs, the whole centre of the body, 
from the mouth to the tail-plate, is seen to be full 
of eggs, to the number of four or five hundred. 
A distinguishing feature also of the sex is the pre- 
sence of a number of star-like patches of brown 
Photo by) [/'. Noad Clark. pigment over the surface of the egg-sac, which 
Wale BOTT oe ean OE Wels have a pretty appearance under the microscope. 
Thiceer Ave. GAL R et EES tele ner ener eee Under natural conditions egg-laying commences 
They take the place of suckers, to attach the parasite about the end of April, and there are at least two 
to the fish, and are also useful in cutting the egg for : 5 : 
Fie TERUG exc? GIL varied. Gitte, broods during the year. Eggs laid late in the year 
GUERESS) remain over the winter and hatch in the spring ; 
but the average time from the laying of the egg until hatching occupies twenty-five days. On one 
occasion an Argulus was observed to have laid over six hundred eggs. The operation of egg- 
depositing, as seen under the microscope, is an interesting one. The three first pairs of legs are 
in motion as usual, the fourth or last pair being held rigid, with their bases (which are rather 
prominent) pressed together over the entrance to the egg-sac and relaxed alternately as each egg 
makes its exit. This done, the Argulus raises her- 
self higher up on the object on which the eggs are 
laid, and moving a little from side to side, places the 
eggs in regular order in ribbon-like rows of from 
three to six broad. The time taken for laying each 
egg is eight seconds. As seen on page 610, the egg 
is oval in shape and pale yellow in colour; each 
one is glued to its neighbour with an albuminous 
material. The eyes of the young Argulus before 
hatching from the egg are clearly visible, being 
relatively large at this early stage. The young 
larva then makes its exit, tail-end first, by cutting 
a longitudinal slit in the egg. Page 612 shows a 
highly magnified photograph of the larva just 
eg emerged. As will be explained later on, this tiny 
i i speck of active life bears but a slight resemblance 
Bei Re Te, to its Tater stages of existence. 
THE SUIMMING FRE OF THE EMALE It immediately sets forth in quest of a host, to 
ARGULUS. which it attaches itself and commences feeding. 
__ The incessant movement of these swimming feet In confinement under artificial conditions, these 
is never arrested during life; mot eyen when the 
Meralns fia attached! to fis Ihest ‘Whe fem patie of newly-hatched larve have been known to live five 
Hook move dimmitonconely (WMegaiice tity trace) days without food. It may seem wonderful how 
