THE ESSEX NATURALIST. 
14 
of head blunt with a pair of very blunt tentacles. The eyes are placed 
wide apart, and a slight constriction is to be seen behind them. The mouth 
lies about two-thirds of the body length from the front margin, and im¬ 
mediately behind the mouth, in the mature individual, a pale streak indi¬ 
cates the position of the sexual organs. The sides of the body are almost 
parallel over the greater part of its length. Posterior to the mouth the 
body margins are frilled. Lobe formula of intestine 16-19, 2 (10-15), 
16-19. 
Habits. Occurs in ponds and in running streams under 
stones and decayed leaves. It can withstand brackish water 
and has been found in the Baltic Sea. 
Bohmig (3) regards the species as a winte~ layer but Stein- 
mann and Bresslau (36) state that it may come to maturity at 
any time of the year. The writer has found sexually mature 
individuals in March, April and August. Probably cocoons are 
produced throughout the year in Britain. The cocoons are 
dark brown, 2 to 3 m.m. in diameter, and contain from 5 to 42 
embryos. The incubation period ranges from two to six weeks. 
Transverse fission has not been observed in this species; its 
power of replacing lost parts is slight. 
Distribution :— 
Britain. Epping Forest, Chigwell Row, R. Stort ; East 
London Waterworks, Tottenham ; Regent’s Park ; Totteridge ; 
Staines ; Rickmansworth ; Elstree Reservoirs. (H.W.) 
Ireland, France, Germany, Switzerland, Italy, Sweden, Russia. 
At present D. lacteum is the only milk-white species of plan- 
arian known in England. It is possible that some of the follow¬ 
ing milk-white planarians may be found, viz. :— Planaria vitta, 
with eyes, and Dendrocoelum infernale and Planaria cavatica, 
without eyes. 
Dendrocoelum infernale Steinmann. 
The species is very similar to D. lacteum, but it is about half the 
length and has no eyes. The uterine duct has an enlargement just 
before opening into the atrium. The uterine duct of D. lacteum 
(Fig. 1. ut.d.) is narrow throughout its course. Intestinal lobe-formula 
15-18, 2 (12-15), 15-18. 
It lives in streams both above and underground. It has not yet 
been found in Britain, but has been recorded from Germany and 
Switzerland. 
Planaria cavatica Fries. 
Synonym. Dendrocoelum cavaticum Enslin. 
Milk-white, without eyes, and with two pointed tentacles. Frontal 
