GENUS HOPLITOPHRYA. 573 



fragments of the posterior region of the body ; as in many Anoplophrya, the hinder 

 of the two zooids may be four or five times smaller than the anterior one and 

 resembles at first sight a bud-development from the same. 



Hoplitophrya securiformis, Stein. 



Body small, elongate-ovate, flattened and widest anteriorly ; the front 

 margin obliquely truncate, often curved to one side and hatchet-shaped 

 the anterior region of the ventral surface bearing a slender horny band, 

 which is bent abruptly posteriorly and extends backwards to the centre of 

 the right-hand margin ; contractile vesicles four or five in number, disposed 

 in a line along the left-hand border ; endoplast slender and cord-like, nearly 

 equalling the body in length. Dimensions unrecorded, but smaller than 

 H. secans. 



HAB. Intestinal tract of Lumbriculus variegatus. 



Hoplitophrya recurva, Clap. & Lach. sp. PL. XXVI. FIG. 22. 



Body elongate-ovate, rounded and widest posteriorly ; the anterior ex- 

 tremity pointed, curved to one side, its ventral face bearing a single 

 corneous uncinus ; contractile vesicle elongate, sinuous, extending nearly the 

 entire length of the body ; endoplast ovate, posteriorly situated. Length 

 1-125". 



HAB. Marine, within the intestinal cavity of Planaria limacina: 

 Norwegian coast. 



As many as thirty or forty zooids of this species were observed by Claparede and 

 Lachmann tenanting a single example of the above-named marine Planarian. It 

 was originally described by these authorities under the name of Opalina recurva. 



Addendum to Opalinida. 



The organisms described by Claparede under the name of Pachydermon 

 acuminatum, found in company with Anoplophrya within the seminal receptacles of 

 Clitcllio arenarius, and supposed to most closely resemble Opalinidas with a distinct 

 and thickened cortical layer, are determined by Professor E. Ray Lankester * to be 

 rope-like aggregations of seminal cells. 



Order II. HETEROTRICHA, Stein. 



Animalcules free-swimming or attached, naked or loricate, entirely 

 ciliate; cilia forming two widely distinct systems, those of the general 

 cuticular surface short and fine, those pertaining to the oral region of much 

 larger size, cirrose, and constituting a linear or more or less spiral or 

 circular adoral or peristomal series ; the cortical layer usually highly differ- 

 entiated, and enclosing an even, parallel series of longitudinally disposed 

 muscular fibrillae. 



* " Remarks on Opalina," 'Quarterly Microscopical Journal,' 1870. 



