360 Miss D. J. Lloyd. Influence of the Position of the 



It is obvious that in cases of incomplete regulation the central nervous 

 system is incomplete in corresponding extent. 



D. If eterom orphic Fo7 > ?ns. 



The culture which produced these forms was one of very short head- 

 pieces where the cut had passed across the anterior part of the brain. The 

 tail-pieces corresponding to these head-pieces also produced new heads. 

 The heteroui orphic forms 20 days after section are shown in fig. IV. In 

 cases where the cut passed obliquely the new heads formed on the anterior 

 end of the cut. This is shown in fig. IV (2). 



Fig. TV. 



1 and 2. Fragment ACC, 20 days. 



A longitudinal section through a heteromorphic form is shown in fig. IX. 

 The rounded shape of the section is due to the contraction that takes 

 place when the animals are dropped into the fixing fluid. It can be seen 

 in the section that about one-third of the complete brain is present. Two 

 well-marked nerves run to the new eyes, and the portion of regenerated 

 gut in the new head shows a beginning of the formation of the three branches 

 characteristic of the front end of the gut of G. ulvce. The gut is full of a 

 dark brown mass of broken-down tissue, and can be seen clearly in the 

 whole specimens. 



E. Regeneration of Nervous System. 



In planarians, i.e., in P. torva (Flexner (3) and Schultz (7) ) and Planaria 

 (Dendroccelum) lactea (Schultz (7) ) the new nervous system arises by cells 

 from the parenchyma crowding round the cut ends of the nerve cords and 

 pushing up among the old nerve fibres, aided possibly by some outgrowth 

 of the old fibres. This is also the method by which G. ulvce repairs injuries 

 to the nervous system. The nerve cords of G. ulvos always show regeneration 

 after a cut, and in every case of tail-formation the new nerve fibres can be 

 found reaching to the end of the newly formed tail at every stage of its 

 growth, and within a few days of the cut joining at the hind end to form the 

 posterior commissure. 



