TAPEWORM PARASITIC IN THE STICKLEBACK. WBA 
staining nucleolus, °0057—-0069 mm. dia. ; often granular strands 
connect the nucleolus to the nuclear membrane. In addition, 
there is a dark-staining “* Nebenkorper” or “ corps lenticulaire ” 
of irregular shape and indefinite size. It seems to disappear 
before the first division and is of unknown significance. Von 
Linstow (14) has figured a similar body in the eggs of Tenia 
longicollis Rud. 
The first division of the fertilised egg (Pl. III. fig. 25) i 
into a vitelline cell crowded with yolk-granules and a “ (Ciel 
zelle,” with nucleus and nucleolus. Kraemer for 7’ jilicollis, and 
von Linstow for 7’. longicollis, figure the vitelline globules as 
isolated, not as being contained in a single cell. 
The d Keimzelle ” next divides into si, and each of these into 
two again, four cells of equal size being formed (PI. ILI. fig. 29), 
°012 mm. dia., with nuclei ‘(005 mm. dia, In van Beneéden’s 
account, these cells are of unequal sizes, two large macromeres 
forming the ‘‘ couche albumineuse,” and two small micromeres 
forming the onchosphere with its membranes and hooks. In this 
case there is certainly a “couche albumineuse” formed (PI. III. 
fig. 31), although as the four cells are identical, it is impossible to 
distinguish those from which it arises. The remaining cells 
divide repeatedly, forming a cellular mass, the nuclei of which 
are of two sizes :— 
(1) nucleus :0057-:0069 mm. dia., nucleolus -0023—-0034 mm. dia. 
Qin. "004-0046 ,, ,, As ‘0011 mm, dia, 
The cells containing the larger nuclei surround the others and a 
split appears between the two (Pl. IIT. fig. 30). This gradually 
widens until the first cells form a definite coat—the second oncho- 
spheric membrane—vound the smaller ones (Pl. IIT. fig. 32). It 
is thus probable that the former correspond to van Beneden’s 
“Chitinogenzellen.” The origin of the hooks and the third 
onchospheric membrane I have not been able to discover. 
The vitelline cell, produced by the division of the ovarian egg, 
does not exist long as a distinct cell, and soon degenerates into a 
mass of yolk-follicles. It is these follicles which scatter when 
the onchosphere breaks through the second membrane (PI. IIT. 
At the time of discharge, the onchosphere is formed of 
number of spherical cells, ‘0057 mm. dia., with distinct nuclei, 
"0034 mm. dia,, the cells at the posterior end being slightly larger 
than those at the anterior. 
When the contents of the majority of the proglottides are 
ready for discharging, the Cestode slightly migrates through the 
intestine, probably by the contractions of the latter, and “hangs 
out of the anus. The egos are then expelled from the uterus 
through a slit caused by a rupture of the ventral body-wall. 
When the contents of the exposed proglottides have been dis- 
charged, the body hangs further out, exposing more segments, 
until all the ripe eggs have been extruded. If stickle- 
g* 
