726 BECOED OF CURRENT RESEARCHES RELATING TO 



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

 transformation of amoeboid movement into ciliary, while the author 

 finds it exactly the same thing during the reverse change. 



Two distinct kinds of organ exist in Convoluta and other Ehabdo- 

 cojles, 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 Convoluta when treated in alcohol a'yellow 

 solution ; and, secondly, large and long spindle-shaped bodies, gene- 

 rally arranged singly, each containing a shar]) brittle needle, of which 

 the point lies close under the apex of the spindle. In a teased prepa- 

 ration they are generally empty, showing tlie 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 generally propelled for 

 some little distance, but sometimes sticks in the mouth of the tube. 

 Gratf's view that these are offensive weapons is certainly the right 

 one, but they are constructed on so distinct a plan from those of 

 Coelenterates that they might better be called sagittocysts than nemato- 

 cysts. 



Below the epidermis lie the circular and longitudinal muscles, and 

 beneath them comes the layer of chlorophyll-containing cells. 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 protoplasm of the cell, which is thus very in- 

 tensely coloured. One, or sometimes two, nuclei are present, besides 

 an irregular heap of granules. It was very difficult to break up the 

 cell completely, and so liberate the granules, but in one or two fortu- 

 nate preparations treated with iodine the blue coloration assumed by 

 many of these granules proved that we have here an actual deposit of 

 starch quite like that which Sachs has shown to take place within the 

 chlorophj 11 granules of the plant. 



Deej)er than the green layer lie colourless granular nucleated cells, 

 which may be spherical or branched. These yield with iodine the 

 red-brown reaction of glycogen very conspicuously indeed. All the 

 internal tissues are bathed in that abundant slimy protoplasm so often 

 adduced in evidence of the infusorian aflSnities of the lower Turbel- 

 laria, which may well serve instead of a special circulatory fluid as 

 well as for digestion, any distinct alimentary canal being absent. 



The development of the generative products is of interest. An 

 apparently ordinary mesoderm cell enlarges and divides into an oval 

 mass of about twelve to sixteen segments. The granular protoplasm 

 of these is gradually drawn out into the very long spermatozoa, and 

 thus each testicular mass is transformed bodily into a bundle of neatly- 

 folded spermatic filaments. The ova are also developed by the division 

 of a mesoderm cell. There are no separate vitellaria, but the yolk of 

 granules seems to arise in the finely granular amoeboid protoj)lasm of 

 the developing ovum. 



Everywhere imbedded in the mesoderm are numerous small colour- 

 less cells scarcely so big as a frog's red blood-corpuscle. These are 

 more or less pear-shaped, with a large central cavity ; and lining one 



* ' Zcitaclir. wiss. Zool.,' xxv. p. 421. 



