FREE NEMATOIDS. 
167 
‘‘Vinegar Eel,” which was met with by Borellus in 1656 ; and 
1 curiously enough the next two chanced to be the “ Paste Eel ” 
j and the Vibrio tritici ; and these three, which have been com- 
paratively familiar to amateur microscopists ever since, remained 
t the only representatives of the family known in this country 
' until within quite a recent period. 
The zoological characters of the family are as follows : — 
Famllt ANGUILLULID^ (Geevais and Vax Beneeen). 
Free Nematoids. — Body cylindrical, tapering more or less at either extre- 
mity. Integument (a) transparent, striated or plain, naked or provided with 
papillae or setae {o!') j often traversed by capillary pores (a'') ; shed and re- 
newed at intervals. Caudal sucker (5) mostly present. Glandular system 
well developed ; often single excretory organ (c) in anterior part of ventral 
region. Lateral lines existing as cellular canals {d) communicating with the 
exterior, with or without a central channel j in others replaced by distinct 
vessels (d'). Median lines indistinct. Nervous system in the form of a gan- 
glionated ring, embracing the anterior part of oesophagus. Ocelli (e), when 
present, aggregations of reddish pigment on anterior part of oesophagus, with 
or without transparent lens-like bodies. Alimentary organs : buccal cavity 
present or absent j oesophagus {g) simple or terminating in bulb-like 
dilatation, separated by constriction from simple cylindrical intestine (7i), 
which is enveloped in a layer of hepatic cells. Generative Organs : 
fe7nale, composed of double symmetrical uteri (k), and short rehexed ovarian 
tubes (J), with vagina (m) near centre of body, but occasionally this more 
posterior and then posterior uterine segment and ovary undeveloped \ ova (n) 
few, large ; oviparous or viviparous : male, consisting of an almost simple 
seminal tube (o), and two equal horny spicules ( jt?), either alone or with one 
or more accessory pieces. 
In this place I will not enter more fully into the anatomy* of 
these animals, but will pass on to subjects of more general interest 
in connection with their physiology and life history. 
The free Nematoids are mostly vegetable feeders. They 
seem to take small quantities of food at a time, consisting 
principally of portions of smaller algae, or of Diatomacese. The 
females bring forth their young at all seasons of the year, even in 
mid-winter. Whether they produce more than one brood seems 
doubtful, although many of them live for six or eight months 
at least. Their power of repairing injuries seems very slight, 
no attempts at repair even seem to be made when their bodies 
have been accidentally divided, although the separated portions 
* Elsewhere I have fully'discussed this part of my subject, in a memoir 
“ On the Anatomy and Physiology of the Nematoids, Parasitic and Free, 
with observations on their Zoological Position and Affinities to the Echino- 
derms.” Phil. Trans. 1866. 
