ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 175 



Light Reactions of Stentor coeruleus.*— S. 0. Mast finds that 

 Stentors free to swim in all directions orient and swim from the source 

 of light. They orient by means of motor reactions, i.e. by turning- 

 toward a structurally defined side, and then proceeding on a new path 

 at an angle with the old one. If a single reaction does not result in 

 orientation it is repeated until the anterior end happens to become 

 directed from the source of light. 



The motor reaction is induced by a sudden increase in light in- 

 tensity regardless of the relation between the direction of the rays and 

 the direction of movement of the animals at the time the intensity is 

 increased. If a source of light to which Stentors are oriented is 

 increased in intensity, the animals respond with tlie motor reaction and 

 are thus thrown out of orientation, but by repeating the motor reaction 

 they soon become oriented again. 



The anterior end is the most sensitive part. The Stentors become 

 readily " acclimated " to light. Once oriented they remain oriented, if 

 the light intensity is not too high, for they are least sensitive to light 

 when the rays strike the posterior end. 



Attached Stentors respond to increase in light intensity by contract- 

 ing or swinging about. They do not orient. 



The light reactions of Stentor, both free-swimming and fixed, cannot 

 be explained by the tropism theory as defined by Loeb, Verworn, or 

 Holt and Lee. 



Structure of Stentor coeruleus. j — 0. Schroder has investigated the 

 myonemes and membranell*. The surface of Stentor is well known to 

 show dark granular " rib-stripes," and light, non-granular " intermediate 

 stripes." Under each of the latter a myoneme runs in a clear canal ; 

 each is a distinct band, sometimes with alternate dark and hght areas, 

 bending inwards at the base, and forming a sort of cone above the foot- 

 place, and running forwards in the other direction as far as the adoral 

 zone. There are no " neurophane " fibrils. The attachment of the 

 membranellae by basal lamellae and basal bands running into the cyto- 

 plasm is discussed. 



New Acinetan Genus.| — B. Gollin describes from the hairs of the 

 thoracic limbs of Eiq)agurus cnanensis Thomson and E. excavatus Herbst., 

 at Cette, a new form, Dendrosomides paguri g. et sp. n. The body is 

 trifurcate, 200-300 ft long, ovoid at the base, and having a long, cone- 

 like, chitinous pedicel. There is a thick external pellicle, and longitudinal 

 striations in the sub-pellicle. The branches carry obtuse digitate lobes, 

 which are terminated each by a fascicle of from 8-15 capitate or non- 

 capitate tentacles. The organism is placed provisionally with the 

 Dendrosomidge. 



Vorticellse on Tadpoles. § — E. Wace Carlier describes a case of 

 tadpoles which bore large numbers of Vorticellae on their skin, and even 



* Journ. Exper. ZooL, iii. No. 3 (1906) pp. 359-99. 



t Arch. Protistenkunde, viii. (1906) pp. 1-16. See also Zool. Zentralbl., xiii. 

 (1906) pp. 714-15. 



X Arch. Zool. Exp6r., Notes et Revue, No. 3, xxxv. (1906) pp. Ixiv.-lxvi. 

 § Proc. Scott, Micr. Soc, iv. (1906) pp. 133-5. 



