5H KARM NARAYAN BAHL 



very largely on the external conditions — temperature, moisture, 

 and the richness of soil. My garden-pots containing the worm 

 were kept quite damp ; the temperature of the hot-house was 

 always about 60° F. and the soil was frequently ' manured ', 

 so to speak ; and it is no wonder, therefore, that under these 

 artificial conditions cocoons were obtained at all times of the 

 year. In nature these conditions are best fulfilled in spring 

 and early summer, and hence we get the greatest activity in 

 egg-laying in these months, although it seems that it does not 

 stop altogether at other times of the year. 



I have opened hundreds of cocoons of Pheretima and 

 feel justified in considering, as a rule, there is only one embryo 

 in a cocoon. Occasionally one comes across two embryos 

 in a cocoon of a very young age, and only once did I see three 

 embryos in one cocoon. In fig. 24, I have tried to represent 

 three typical stages of the embryo of Pheretima in their 

 natural size (the external segmentation of the body, although 

 complete throughout, cannot be made out with the naked 

 eye and is therefore not represented). 



The rate of development is very much slower in Phere- 

 tima than in Lumbricus. Wilson (18) found that in 

 laboratory cultures the young worms (Lumbricus) made 

 their escape from the capsule in about two or three weeks. 

 Beddard (3) judges that the shortest time in Acanthodrilus 

 can hardly be less than five or six weeks. In Pheretima 

 the rate is even slower than that in Acanthodrilus, and 

 I cannot put the shortest period at less than eight weeks in 

 this case. 



Beddard (3) found that the albuminous fluid filling the cocoon 

 in Acanthodrilus, as in Lumbricus rubellus, was 

 milky and opaque while the shell was transparent ; in Phere- 

 tima, however, the albuminous substance of the cocoon is 

 perfectly clear and transparent like its shell, so that under 

 a binocular microscope I could always see, by transmitted 

 light, the embryo inside the cocoon without opening it, and 

 it was thus very convenient to be able to know roughly the 

 size and age of the embryo before opening it. 



