l\vo Neiv Species of ChaetogaHter. 9H 



Reproductive Si/stem. 



I could not discover any trace of reproductive ort:^uiis in any 

 specimen I examined. Asexual reproduction is, lioAvcjvur, very 

 common; in fact, a normal individual without any trace of fission 

 is not at all common. 



Asexual Iteprodaction . 



Mr. H. Seddon, L.V.Sc, of the Veterinary School, and Mr. J. 

 Brake, B.Sc, of the Biology School, were good enough to take some 

 niicro-photogi-aphs of C. australis during fission, and draAvings from 

 tliese are reproduced in Figs. viii. to xvi. 



Normally, asexual reproduction begins to take place when the 

 animal consists of about 12 segments. But actual fission does not 

 take place till more segments have been added on each side of the 

 line of fission. The process may be artificially hastened, is not 

 actually brought about by heat, scarcity of water, or treatment with 

 some foreign material, e.g., methyl blue in small quantities, or some 

 other water stain, if very dilute solutions are used; if the solution 

 be too strong, or the water begins to dry up through evavoration too- 

 quickly, the animal disintegrates at once. This had to be borne in 

 mind while the photographs were being taken, and plenty of water 

 given the animals. 



The first indication that fission is about to take place, is a thicken- 

 ing and wrinkling of the body wall about the region of the eighth 

 segment. At the same time outgro^vths from the ventral nerve 

 cord grow up either side of the alimentary canal, under the 

 thickening, about the line of future fission, and finally form a nerve 

 ring round the alimentary canal. The thickening is at first fairly 

 wide (Fig. viii.), but later it narrows to form just a line across from 

 side to side. For a long time the animal remains at this stage, 

 indicated in Figs, x and xi. ; this almost has the appearance of 

 disintegration, but the actual animal these photographs were taken 

 from divided after this stage, and formed two new individuals very 

 like those represented in Fig. xvi. With regard to the organs, the 

 canal becomes differentiated to form the new parts of the new indi- 

 viduals. That is, the intestine of the original individual lengthens, 

 and finally becomes divided and differentiated to form the whole 

 canal of one of the new individuals; and the stomach of the original 

 individual, with a small part of the intestine, lengthens, and finally 

 becomes stomach and intestine of the second new individual; so for 

 a time the mouth and the anus of the two new individuals are in 



