FRIEND: ON HYBRIDITY AMONG WORMS. 393. 
have something to do with the question of sexual intercourse. Not 
one of the many writers whose works I have been able to consult 
has given a satisfactory reason why the brandling, and several other 
species, pour out at certain times from their dorsal pores a peculiar, 
and in some cases ‘highly pungent, fluid. I have been able, by the 
careful study of this subject, to do something towards a solution of 
certain problems which this fact involves. I have also found that 
our indigenous species fall naturally into certain groups or divisions, 
and that each division is marked by its own peculiarity in the matter 
of secretions. No true Zumbricus secretes turbid, highly-coloured, 
or feetid fluids. In he genus A/lolobophora several species of the 
Dendrobeenic group exude such a secretion, but the mucus 
differs from that of the earthworms, while the Lumbricoid 
Allolobophoras more nearly approach the typical genus. Another 
group is capable of secreting offensive fluids—such, at any rate, they 
prove to most anthropoid nasal organs—while yet another secretes 
fluids which are destitute of any strong odour. Since the worms can 
smell and taste, they can detect the presence of anything peculiar 
which affects these ee and thus, without doubt, each group can 
identify its own member 
Here, however, es vided ntity seems to end. How can one 
Limbricus determine whether another Zumdéricus does or does not 
belong to the same species? There are at present four known 
species* of Zumbricus in Britain, and what is to prevent these 
Species intermingling? This is a very eel question. It may 
be answered, in the first place, that there is so wide a difference in 
size between the largest species (Z. ferrestris Linn.) and the smallest 
(Z. purpureus Eisen), that the two are as unlikely to mate as = 
tiger and the cat might be if living in the same forest. In the ne 
place it may be asserted that the largest species usually affects tk 
garden or arable soil, while the medium-sized species are foun 
chiefly in fields, and therefore are seldom coming in each other’s 
way. We must admit the truth of these replies, and still there is 
room for at least three forms of hybridity. Thus we find in the same 
localities three species of Lumbricus, any two of which may pair. 
This would give us the following results :— 
(1) Lumbricus rubellus + rubescens. 
(2) Lumbricus rubellus + purpureus. 
(3) Lumbricus rubescens + purpureus. 
Denar oe 
*I exclude Lumbricus eisent Levinsen, because, though it occurs freely in 
England, i it does not properly belong to this genus, and may yet prove to be a type 
of a new genus altogether. At present I class it among the Dendrobene 
Oct. 1892. 
