Haswett—A Monograph of the Tennocephalee. 131 
sometimes by discharge of spermatozoa and of the secretion of the “prostate” glands. 
I have never observed the act of copulation; but I have found in many specimens the 
uterus and oviduct to contain actively-moving spermatozoa; in some of those the 
uterus and oviduct were undergoing strong peristaltic contractions, tending to drive 
the spermatozoa forward. In such specimens, before an ovum has become discharged 
from the ovary and impregnated, the large sac usually termed receptaculum semints 
is greatly distended with a mass of yellowish semi-fluid material. This consists 
mainly of the secretion of the yolk glands, but in the midst of it may be seen here 
and there movements indicating the presence of spermatozoa; apparently the overplus 
of spermatozoa, and very possibly that of the secretion of the prostate glands, forms a 
contribution to the accumulating mass of yolk. The so-called veceptaculum semtnts 
is thus more correctly to be termed veceptaculum vitell. When it is full its contents 
form a bulk the size of the uterine egg. In the next stages which I have observed 
this mass of yolk has become transferred to the uterus enclosing the impregnated 
ovum, which has meantime become discharged from the ovary—the vreceptaculum 
viteli in such a specimen being contracted and empty. The mass of yolk, with the 
impregnated ovum, is of great relative size and greatly distends the uterus, displacing 
the neighbouring parts to a considerable extent. Here it becomes enclosed in a 
chitinoid shell. 
Considerable variation occurs in the form and mode of attachment of the egos 
in the various species. In 7. Nove-zealandie the somewhat pear-shaped eggs are 
attached by a short stalk connected with the narrower end, and when the embryo is 
mature the shell is ruptured by an annular dehiscence, so that a sort of lid is separated 
off and a goblet-shaped body remains attached to the crayfish. The same holds good 
of 7: minor. In 7. fasctata numbers of the oval eggs adhere together and to the 
surface of the crayfish by means of a layer of hardened secretion in which they are 
embedded ; they lie flat on the surface, and on one side about the middle there is a 
short, slender stalk, which, however, does not serve for attachment. 7. guadricornis 
presents a similar arrangement; the egg is much broader at one end than at the 
other, and towards the end is a rudimentary stalk. In 7: Semper there is only a 
shght rudiment of a stalk, and the eggs are cemented singly to the surface by one side, 
Monticelli* describes in a species of Zemmnocephala which he regards, though he 
does not give his reasons for the determination, as 7. chz/ensis, a very remarkable 
arrangement of the ova. They are pear-shaped, and a slender, flexible stalk of varying 
length connects them together two and two by the narrow ends ; an operculum was 
not observed. 
* “ Breve nota sulle uova e sugli embrioni della T'emnocephala chilensis Bl.” ‘ Atti della Societa Italiana di scienze 
naturali,’ Vol. XXXII. 1889. 
