Pressure upon the Regeneration o/Gunda ulvse. 5 



Fig. 4. 



A. — Ovary 



B. — Ovary after 25 days' regeneration of posterior end in sea-water. 



g., gut. pa.c, parenchyma cells, ov., ovary, ov.d., oviduct. 



(b) Growth. 



Experiments were also made in rate of growth. Worms which had been 

 reduced to 1*5 mm. in length by a long period of starvation were fed daily 

 on scraps of the tail muscle of shrimps. The rate of growth was very rapid, 

 and is indicated in curve B, in fig. 1. Unfortunately the experiment was 

 interrupted, and the worms went without food from the 25th to the 37th day. 

 It can be seen that this period was one of reduction in length. On the feeding 

 being resumed growth again took place. 



At the beginning of the experiment the worms were without a trace of the 

 generative system. This was first noticed in the sections at the 10th day, i.e. 

 when the worms were 2 - 7 mm. long. The generative system was completely 

 restored at a length of 4 - 6 mm., i.e. 36 days after its first appearance. The 

 generative system in Gunda, as in other Turbellaria, is formed by the localisa- 

 tion and metamorphosis of nests of parenchyma cells. 



III. Preliminary Experiments on Duration of Life of Whole Animals 

 in Solutions of Different Osmotic Pressure. 



A preliminary series of experiments was made so as to ascertain the limits 

 of density, salinity, and osmotic pressure which whole worms are capable of 

 withstanding. A table recording these results is given below (Table II). 

 Conditions under which the worms can live for seven weeks were taken as 

 capable of supporting them alive indefinitely. 



