ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 457 



like mouth, extending almost right across, and showing short, rigid, 

 buccal threads and pharyngeal trichites. 



On each side of the animal there are stinging papilla?, projecting 

 like guns from a frigate, about a score altogether. There are also 

 reserve trichocysts scattered on the ectoplasm. There is a large posterior 

 contractile vesicle. The nucleus is horseshoe-shaped, filled with micro- 

 somes and a number of nucleoli. There is also a pale micronucleus. 



The Infusorian is carnivorous, and shows a preference for a Rotifer 

 ( Diplax trigona) ; the Rotifer's eggs and fat-globules may be seen in- 

 side. It swims slowly, and the long anterior cilia appear to be of most 

 importance. It is a very delicate animal, difficult to keep in captivity. 

 A transverse division was once seen. 



Sometimes this strange Infusorian passes into a resting phase. It 

 is seen to be surrounded by a radiation of long tentacle-like processes. 

 These are transformed stinging papilla?. The trichocysts are grouped 

 in a crown at the apex, and some migratory trichocysts may be seen 

 making their way up the stalk. 



The author gives a detailed description of the trichocysts. They 

 are minute curved rods 8-9 ,u in length, 1 p. in transverse diameter. 

 They can move or are moved about, and they pass up into the papillae. 

 They may accumulate at the base and " wait their turn " to pass up to 

 the tip. They arrive at their place with their distal end in front, which 

 is the proper disposition for the future explosion. It is possible that they 

 are transported by movements of the plasma. 



The stinging papilla? are the only offensive organs. The trichocysts 

 do not act except from them. They may be compared to mitrailleuses. 

 In explosion a fine clear thread emerges from the trichocyst, and at the 

 end of it a minute nervous spherule with an acid reaction. It is possible 

 that there is an evagination of a tube from within the trichocyst, and 

 that a poisonous drop emerges by a rupture of the extreme tip. 



Diplodinium ecaudatum.* — R. G. Sharp has made a study of a 

 Protozoon which is found in the stomach of Ruminants. In the course 

 of his study he discovered three new forms, with respectively two, three, 

 and four posterior spines, but otherwise similar in structure to Diplo- 

 dinium ecaudatum, D.caudatum (one spine), and D. catteria (five spines), 

 the six forms making a complete series. With the exception of the 

 primary spine, spines of all sizes are to be found, ranging from mere 

 nodules up to spines which are equal to one-third of the entire length 

 of the body. In every case of division observed, animals with a certain 

 number of spines gave rise to two daughter-animals, each of which 

 was provided with the original number of spines. But none of these 

 divisions, as far as Avas observed, followed at once after conjugation, and 

 it is possible that division immediately following conjugation might 

 have resulted differently. The presence of one of these forms in the 

 stomach of the ox in no wise necessitates the presence of other forms, 

 but the two-, three-, and five-spined forms were never found except 

 when the four-spined form was also present. Revised in the light of 

 the discovery of these new forms, the valid species in the genus are 



* Univ. California Pjblications (Zool.) xiii. (1913) pp. 43-122 (5 pis. and 4 figs.). 



