Haswett—A Monograph of the Temnocephalee. 133 
1, TemnocePHALa FasciaTa. Plate x. figs. 1-3, 5 and 6, 13-16; Plate x1. figs. 2-4, 8 and 
9; Plate xu. figs. 1, 4-6; Plate xi. figs. 12-14; and Plate xiv. fig. 1. 
Temnocephala fasciata, Haswell, l.c. p. 284, pl. xx. figs. 1 and 2. 
This is one of the largest forms, attaining sometimes, when extended, a length of 
more than half an inch. It is also one of the most highly organised. 
The body is strongly pigmented on both dorsal and ventral surfaces, the 
former being much the darker. The principal layer of pigment is situated below 
the basement-membrane of the integument, and superficial to the layer of longitudinal 
muscular fibres, and is arranged in an exceedingly fine and close network; but pigment 
also occurs on a deeper plane, internal to the longitudinal muscular layer. There are 
five subequal slender tentacles. The intestine presents a considerable number of 
constrictions with transverse muscular bands (“septa”). The testes are somewhat 
oval in shape, the anterior situated nearly opposite the middle of the intestine, the 
posterior nearly opposite the genital opening. The cirrus is strongly curved, and 
has a very definite introvert, which is considerably thicker than the part of the cirrus 
immediately preceding it; it contains a large number of close-set, stout, pointed spines. 
The vitelline glands spread over the dorsal surface of the intestine and extend also 
some distance on the ventral surface; their lobes have a tendency to become arranged 
in transverse rows. There are no teeth in the vagina. 
Temnocephala fasciata occurs on the surface of the widely-distributed A stacopszs 
serratus, the largest of the Australian crayfishes; and I have obtained specimens of 
the parasite from various parts of the Blue Mountains, as well as from streams in the 
coastal districts from the Richmond River in the north to the Yarra in the south. I 
have never noticed a live specimen of the crayfish, small or large, recently removed 
from the water that did not harbour more or fewer specimens of 7. fasczata. Usually 
there are many dozens on each crayfish. The specimens of Astacopsts serratus from 
different localities differ a good deal as regards colouration and other minor points; 
but except as regards slight differences in the arrangement of the lighter and darker 
zones, which does not always conform to the description previously given by me, the 
Temnocephale present little appearance of variation. 
Together with Zemnocephala fasciata, and closely resembling the young of that 
species, were found two examples of a distinct form. They were both very small, 
only about 2mm. in length, but were in a much more advanced stage of development 
than are the young of 7. fasczata when of that size. In the latter the reproductive 
organs are entirely undeveloped. In the form under consideration, though there 
were no fully developed spermatozoa and the ovary was not seen, the male repro- 
ductive ducts with the vesicula seminalis and cirrus were fully formed, as were 
