210 Proceedings of the Royal Physical Society. 



of the great variety of ways in which contraction may take 

 place. 



9. The circulation of protoplasm, which has so long 

 been known and studied in such plants as Ghara, Nitella, 

 Vallisneria, etc., and which is believed to be of very wide 

 distribution in vegetable cells, though little searched for 

 in the animal kingdom, has been observed * in the cartilage 

 cells of Geryonia. Unfortunately, no observations have 

 been made upon the still more remarkable phenomenon of 

 " aggTegation of the protoplasm," discovered by Darwin f 

 in the cells of the glands of Drosera, and observed by him 

 also in the sensitive hairs of DioiicBa and in the roots of 

 various plants, save a single confirmatory paper by Francis 

 Darwin;:}: and it still remains to be investigated whether 

 this remarkable process takes place in animal cells, whether 

 it is related to circulation, and whether both are modifica- 

 tions of that irregular streaming which may be observed 

 within the body of an amoeba. Perhaps these phenomena 

 may have something in common with those movements of 

 the nucleus in animal cells above referred to; in any 

 case a thorough comparative study of all these modes of 

 protoplasmic motion is highly desirable. 



10. In this relation, too, the contractile vacuoles of many 

 zoospores, infusorians, etc., are worthy of attention. It has 

 long ago been pointed out how the irregular disposed and 

 non- contractile vacuoles of the lowest amoeboid organisms 

 become differentiated on one side into the large sap cavities 

 of vegetable cells, and on the other into the regularly con- 

 tractile vacuoles of many Protozoa. The most remarkable 

 specialisation, however, is certainly that which I have recently 

 described in Pulsatella § (see section 8, supra). 



11. The coalescence of many amceboid cells into a continu- 

 ous mass or Plasmodium was discovered by De Bary to be 

 a regular stage in the life-history of the Myxomycete fungi. 



* Gegenbaur, Comparative Anatomy, p. 26. 

 + Insectivorous Plants, London, 1877. 



X Aggregation in the Tentacles of Drosera (Quart. Jour. :Micro. Sci., xvi., 

 1876). 

 § 0^}. ci(, 



