368 
tozoons from one to another proglottis: a very important circum- 
stance in case, if any of the proglottides were not fertilized imme- 
diately! Occurs in two different forms, as forma major (Fig. 2) 
and forma minor (Fig. 1). Hosts: Urinatores. 
The new species of this new genus is characterized as follows: 
Tatria biremis sp. nov. Maximal total length of body — 1,9 mm. 
maximal breadth — 0,7 mm. Length of rostellum (Fig. 3) about 
0.41 mm. Number of hooks (Fig. 4) on its apex — 10. Their 
length — 0,044 — 0,050 mm. Number of rings (Fig. 3) of little 
hooks (long 0,004 mm.; Fig. 6) about 30. Suckers and the posterior 
half of the head eovered with minute spines (about 0,0012 mm. 
long; Fig. 5). Maximal number of proglottides 30, the last, 1—4, of 
them only include oncosphaers with hooks. Number of testicles — 7 
(Fig. 8, 10). Receptaculum seminis near the anterior border of 
the proglottis (Fig. 9, 10, 12). Longer diameter of oval embryo 
(Fig. 21) -—- 0,02 mm. Length of embryonal hooks — 0,008 mm. 
Host: Podiceps auritus Lath. 
Here may be mentioned still some other details, eoncerning 
the tapeworm in question. not evident from the diagnosis eited 
above: 
Of the five systems of muscle fibers, characteristie for the Aco- 
leinae, could be found in T. biremis only two longitudinal ones 
(Fig. 15). The testicles are divided by the yolk gland in two 
groups. One of them including three testicles lies on the same side, 
on which also lies the eirrus pouch, the other on the opposite side 
(Fig. 7, 8. 10). The first or inner of two seminal vesicles is sur- 
rounded by a layer of glandular (prostatie) cells (Fig. 10). The 
fecundation proceeds here as usually in the Acoleinae, i. e. by 
direetly perforating (on the dorsal surface) the wall of the body 
and squirting the sperm in the receptaculum seminis (Fig. 12, 15, 17). 
The wall of the uterus becomes gradually thieker (Fig. 18) and 
in the mature proglottides, ineluding oncosphaers with hooks, it 
attains such a degree of thickness as shown by Fig. 2 (two last 
proglottides) and Fig. 19. This overgrowth (hypertrophia) accom- 
panied by fatty degeneration of the old proglottides helps pro- 
bably towards freeing the include eutieular (Fig. 20) sac from 
oncosphaers. 
The other anatomical details and also the difference between 
both the forms, which oceur here, are evident from the adjoined 
