!)2 MR. H. CHARLTON BASTIAN'S MONOGRAPH 



readily recognizable. The exact structure of the pharynx and oesophagus, the nature of 

 the integumental markings or stria3, and the position and character of the duct of the 

 ventral gland seem to me the other characters which, from their constancy, should be 

 most relied upon in the construction of genera. The necessity of absolute accuracy con- 

 cerning these details cannot be too strongly enforced, in view of the crude generalities 

 which have been offered by some preceding observers as specific descriptions, many of 

 which are absolutely useless as a means of identification, and serve only to swell the 

 number of synonyms and uselessly perplex subsequent workers in the same field of 

 I'csearch'. 



Family ANGUILLULID^, Gervais & Van Beneden. 



Free Neinatokls. — Body cylindrical, tapering more or less at either extremity. In- 

 tegument transparent, striated or plain ; naked, or provided with papillae or setae ; tra- 

 versed by capillary pores ; shed and renewed at intervals. Caudal sucker mostly pre- 

 sent. Glandular system well developed; often single excretory organ in anterior part 

 of ventral region. Lateral lines existing as cellular canals communicating with the 

 exterior, with or without a central channel ; in others replaced by distinct vessels. 

 Median lines indistinct. Nervous system, none. Ocelli, when present, aggregations of 

 reddish pigment on anterior part of oesophagus, with or without transparent lens-like 

 bodies. Generative organs — -female, composed of double symmetrical uteri and short 

 reflexed ovarian tubes, with vagina near centre of body ; vagina occasionally more poste- 

 rior, with posterior uterine segment and ovary undeveloped ; oca few, large : male, con- 

 sisting of an almost simple seminal tube, and two equal horny spicules, either alone or 

 with one or more accessory pieces. 



' The best method of detecting and capturing these animals I have found to consist in separating with ordinary 

 microscopical teasiiig-needles the specimens of algae or coralline into small fragments, on the surface of a square piece 

 of glass covered with a thin stratum of fluid, the glass being laid either upon a black surface or, better still, upon a 

 small mirror, when the larger species may be recognized with the naked eye, and the smaller with an ordinary watch- 

 maker's lens. They are best captured by taking them up upon the pointed extremity of a feather. I have employed 

 an ordinary quill pen, with its upper extremity cut off obliquely. In the case of marine or freshwater mud, it should 

 be spread out with a little water into a very thin stratum, when, in a minute or so, various spots of disturbance will 

 indicate the position of these or other minute animals. 



I am indebted to the kindness of my friend Howard Fox, Esq., of Falmouth, for being able to pursue in this inland 

 locality (Broadmoor, Wokingham) researches concerning the marine Nematoids commenced at Falmouth, since he 

 has abundantly supplied me at various times with mud, sand, and algse from the estuaries and tide-pools of that place. 



