454 



Mr. P. Geddes. Observations on the [Mar. 27, 



to the unaltered cilia, and I have even seen the finer pseudopoclia con- 

 tracting gently in time with the cilia of the same cell, thns establishing 

 a complete gradation between the rhythmically contractile cilium and 

 the amoeboid psendopodhim through what is really a rhythmically con- 

 tractile pseudopodium. Hasckel and others have accumulated many 

 instances of the transformation of ciliary movement into amoeboid and 

 vice versa, bat I only know of one case in which the passage-form, the 

 cilium-like pseudopodium, has been actually observed. Lankester,* 

 speaking of developing spermatozoa of Tub if ex, describes "very large 

 active fusiform masses, exhibiting very rapid movements like a cilium, 

 and possessing at the same time the character of a pseudopodium." It 

 is important that Lankester's passage-form occurred during the trans- 

 formation of amoeboid movement into ciliary, while I find exactly the 

 same thing during the reverse change ; and it is not improbable that 

 such ciliary pseud opodia may transitorily occur in many cases. 



Perhaps no animal structure has received more varied and contra- 

 dictory interpretations than the rod-like bodies (Stdbchen, baguettes) of 

 the Planarian integument. " Max Schultze holds them for end-organs 

 of nerves, Leuckart and many others for nettle-capsules, Schneider for 

 sjpicula amoris, Keferstein for mucous glands, Graff for more or less 

 developed nematocysts."f Two distinct kinds of organ exist in 

 Gonvoluta and other Khabdocceles, and have been confused under the 

 same name ; first, the heap of coloured rod-shaped bodies, the original 

 " Stabchen " of Max Schultze, which furnish in Gonvoluta the yellow 

 solution already referred to, and, secondly, large and long spindle- 

 shaped bodies, generally arranged singly, each containing a sharp brittle 

 needle, of which the point lies close under the apex of the spindle. 

 In a teased preparation they are generally empty, showing the tube in 

 which the arrow lay, and with a little granular protoplasm hanging 

 round the mouth like the smoke of the explosion. The dart is gene- 

 rally propelled for some little distance, but sometimes sticks in the 

 mouth of the tube. Graff's view % is certainly the right one, that 

 these are offensive weapons, but they are constructed on so distinct a 

 plan from those of Coelenterates, that they might better be called 

 sagittoeysts than nematocysts. True nematocysts have been described 

 in some other Planarians. 



Below the epidermis lie the circular and longitudinal muscles, and 

 beneath them comes the layer of chlorophyll- containing cells. These 

 are clear and semi-fluid, more or less irregular in shape, but becoming 

 spherical when separated. . The chlorophyll is not collected into 

 granules as in the higher plants, nor into drops as in the green 

 cells of Vortex viridis, but 'is diffused throughout the whole pro- 



* " Quart. Journ. Micro. Sci.," 1870, p. 292. 



f Minot, " Studien an Turbellarien," " Semper's Archiy," III, 4, 1877. 

 X " Zeitsch. f . "w. Zool.," xxt, p. 421. 



