631 



ON FIVE NEW SPECIES OF THE GENUS 

 HABROTROCHA. 



By David Bryce. 

 {Read October 26th, 1915.) 



Plates 38 and 39. 



In the following paper I describe five new species of pellet- 

 making Rotifera, which are to be added to the already important 

 genus Habrotrocha. The first two, H. insignis and H. sylvestris, 

 may be said to belong to the central group of the genus, being 

 closely related to H. angusticollis (Murray), which has been 

 designated as type species by Woodcock.* The characteristics 

 of this central group consist of a relatively long and slender 

 head and neck, a middle body distinctly stouter, and an exceed- 

 ingly short foot, together with rather narrow trochal disks borne 

 on somewhat high pedicels usually adnate. H. insignis has 

 other more special characteristics, one of which has not been 

 seen in any other Bdelloid. The upper lip, when closely exam- 

 ined, is found to have a curious stiffening, apparently that it 

 may better support the slender pedicels under the strain of 

 the lashing cilia above. This stiffening is not very obvious, 

 but once observed is readily recognised and can be detected even 

 when the corona is retracted within the mouth. 



A second interesting structure is the looping of the gullet in 

 a certain position of the body. A similar structure has been 

 already noted by Zelinka for Habrotrocha Leitgebii, and it is also 

 present in two of the other new species, viz. U. sylvestris and 

 H. flava. The looping of the gullet is one of several structural 

 modifications that are distinctly connected in their origin with 

 the attitude assumed by the rotifer when it is feeding. There 

 are some Bdelloids of the family of the Philodinidae which feed 

 without attempting to extend themselves, but others extend 

 themselves habitually to the utmost, without doubt in order to 

 * Woodcock, Int. Cat. Set. Lit., vol. x., 1911. Zoology, vi. p. 45. 



