302 
Part III — Eighth Annual Report 
there is little or no current. It is not necessary in this paper to describe 
the structure of the male and female reproductive organs of the skate, for 
BUCh descriptions can be found in any of the common text-books of 
practical zoology. It may, however, be well to recall the fact that the 
purse is formed by a special glandular portion of the oviduct, but whether 
the process of its formation begins before or after the arrival of the egg 
in the oviduct is not easily decided.* 
Wyman (p. 32) has already expressed the opinion that the purse is 
partly formed before the egg leaves the ovary. 
From many circumstances I have also long inclined to this view. ( )ne 
often finds part of a purse in the oviduct and no yolk or egg within it. 
It appears very likely, nay, almost certain, that the lower half of the 
purse is formed before the egg arrives at the oviducal gland, and that 
after the arrival of the egg the closure of the purse is at once effected. 
My conclusions on this matter were confirmed by a circumstance noted, 
regarding some shark purses which came into my hands. These were all 
perfectly formed, and had been laid ; that is, they had not been taken from 
the present shark. Fully ten per cent, of those purses, though quite 
intact and closed up, contained no egg. White was present, but no trace 
of a yolk. The only explanation I can give of this circumstance is that 
no egg arrived from the ovary in time for reception in the partly formed 
purse, and that the purse was completed without ever having contained 
a yolk. These abnormal purses were laid in the confinement of an 
aquarium, and I cannot say that anything of the sort has come under my 
notice among the ray-purses in my possession.! 
Fertilisation must be effected in the upper limit of the oviduct. 
Of the blue skate (R. batis), Day (vol. ii. p. 336) says that they are 
stated to generate in March and April, and that the purses are cast from 
May to September. According to Parnell, the young appear in the follow- 
ing spring. 
I can confirm and extend these statements. On referring to my lists I 
find that the greatest number of purses was received in March and April, 
and that many of them were only just formed. Purses naturally deposited 
have never come into my possession. 
For this species of skate I can, however, much extend the period of 
reproduction, for I have received purses of R. batis in all months of the 
year ; certainly but few in winter and most in the spring. 
Hence we must say of the blue skate that the chief time of reproduc- 
tion is in the spring months, March and April, but that some eggs are 
developed and fertilised in all the other months of the year. 
Of the thornyback skate (R. clavala), Day says that it is found in 
shallower water than the blue skate. This I also found to be the case. 
In the fishing villages on the Firth of Forth it is the form which is caught 
nearest inshore. ' It begins to germinate in June, and brings forth its 
young (? eggs) in July and August f (Tennant). Much more correct is 
the statement of Couch, that the eggs are deposited in May and June. 
I can say little of the existence of winter breeding in thus form, for 
until January I received no thornyback purses ; from this month they 
were obtained in increasing numbers until June. In Holland this skate 
is caught in abundance in June, and during that month great numbers of 
thornyback purses may be found in the fishing boats. After being caught 
the fish have deposited their purses in the boat. 
* Never more than two eggs, one in each oviduct, are found in a single skate. 
t Since this was written I have met with one completely formed and closed purse 
of B. radiata, which contained no yolk, and another of B. batis also destitute of a 
true egg. 
