518 SUMMARY OF CURRENT RESEARCHES RELATING TO 



well-marked correlation exists between the position of the girdle, on> 

 the one hand, and the number (a) of collector nerves, (6) of post-girdle 

 nerves, and (c) of whole vertebrae. None was found between the number 

 of the fin-rays and the number of fin-nerves. 



At certain stages in ontogeny the number of collector nerves and 

 of post-girdle nerves is greater than in the adult ; the most caudal two 

 or three form a posterior collector, never found in the adult. 



" The different variations observed are not discordant with the view 

 that the limb is capable of migrating along the body, on which view 

 it must be supposed that a secondary rostral migration has followed a 

 primary caudal one. Moreover, such a view receives confirmation from 

 the existence of a posterior collector and of a more extensive anterior 

 collector in certain embryonic stages." 



Structure of Amphioxus.* — Dr. H. Joseph has made some new 

 observations on various points connected with the minute anatomy of 

 Amphioxus. He finds that the different staining reactions given by the 

 epithelial investment of the primary and secondary gill-bars depend 

 only upon their physiological relation to the ccelomic fluid. A re- 

 markable abnormality of development in the branchial skeleton of a 

 female specimen found at Naples is also described in detail. The 

 abnormality is similar to one previously found by Benham. 



Significance of Spiral Swimming.f — H. S. Jennings points out 

 that swarm-spores, flagellate and ciliate infusorians, rotifers and many 

 other lower organisms, as they pass through the water, revolve on their 

 long axes, and thus follow a course that takes the form (as a rule) of a 

 spiral. To understand the significance of this was perhaps impossible 

 until the relation between it and the method of reaction to a stimulus 

 in these organisms was known, and especially until it was recognised 

 that the body of the organism bears a constant relation to the axis of 

 the spiral, — that is, that the same side of the organism is always 

 directed towards the outside of the spiral. This was pointed out by 

 Jennings in previous studies. 



It seems that the device enables the organism to follow a course 

 which is practically a straight one ; without such revolution many 

 creatures merely describe small circles, making no progress. By means 

 of the revolution, the organism compensates with absolute precision 

 for any tendency or combination of tendencies to deviate from a straight 

 course in any direction. 



INVERTEBRATA. 



Fauna of Baikal-Lake.J — Prof. A. Korotneff gives a brief report 

 on the results of an excursion to this interesting lake. Sponges were 

 represented by four species of Lubomirskia (with no gemmules), a 

 species of Ephydatia, and Spongilla microgemmaia sp. n. 



Many specimens were obtained of the large slug-like Dicotylus 

 (Planaria) pulvinar, of which Grube got only one; a description is 

 given, and a new name, Bimacephalus bistriatus. A new fresh-water 



* Arbeit. Zoo]. Inst. Wien, xiii. (1901) pp. 125-54 (2 pis.). 

 t Amer. Nat., xxxv. (1901) pp. 3G9-78 (11 figs.). 

 J Biol. Centralb., xxi. (1901) pp. 305-11 (1 fig.). 



