146 REPORTS ON INVESTIGATIONS AND PROJECTS. 



were operated on at various levels, as follows : A portion of the nerve-cord 

 was removed from 102 worms ; a portion of the intestine was removed from 

 26 worms; controls, 151 worms. 



After ordinary amputation, regeneration was first observed about the fif- 

 teenth day. After removal of the nerve-cord, 23 or more days were required 

 before regeneration was observed. In spite of the large mortality among 

 worms with the nerve-cord removed (40 per cent), and though enough time 

 was not given for some of the more seriously injured ones to regenerate, 

 about 37 per cent of the animals did regenerate a perfectly differentiated 

 head, segments, and series of complex appendages. 



The worms were prepared for further examination of the operated region 

 in order to ascertain definitely whether the nerve-cord had been regenerated 

 in the interval. It is highly probable, on the basis of studies on Lumbricus, 

 that the head and segments of Amphinoma regenerated in the continued 

 absence of motor stimuli, exerted by or through the nerve-cord. 



A NEW METHOD FOR THE PRODUCTION OE EUSED EARV^. 



The Herbst-Driesch method for the production of fused embryos and 

 larvae has been used by several American investigators with Arbacia eggs, 

 without positive results. The writer succeeded only after modifying this 

 method as described in a recent publication. Neither the original nor the 

 modified methods were effective with sea-urchins common at the Tortugas, 

 namely, Diadema, Toxopneiistes, and Hipponoe. 



With Toxopneiistes eggs the following method was finally used, which 

 gave rise to large numbers of fused plutei and which involved no disturbing 

 physical changes as with former methods. After fertilizing the eggs, they 

 were placed in sea-water, to which enough 5/8 molecular NaCl was added 

 to make solutions ranging between 35 and 75 per cent ; for example, a 35 per 

 cent solution consists of 75 c.c. of 5/8 molecular NaCl added to 125 c.c. of 

 sea-water. The eggs were left in this solution about 6 hours and were then 

 transferred to normal sea-water. The unfused larvse floated to the surface, 

 the fused ones remained at or near the bottom. 



I am unable at this time to give an exact statement of the number of fused 

 larvse produced in this way, though it appeared that it greatly exceeded the 

 number obtained with Arbacia. If on further examination this is found to 

 be correct, the method above outlined can claim the distinction of pro- 

 ducing the largest number of fused echinoid larvse on record. The types of 

 fusion were essentially the same as those heretofore described. 



Whether the other echinoid eggs could be made to fuse by the same 

 method was not determined, on account of the absence of sufficiently ripe 

 eggs and sperm during the months of July and August. 



VARIATIONS IN ECHINODERM LARV.^ INDUCED BY CHEMICAL AND 



PHYSICAE CHANGES. 



The present inquiry undertook to determine to what extent the number 

 of variants under normal conditions would be increased or new variants 

 produced, and under what conditions maximum and minimum effects would 

 appear after shaking or centrifugalizing eggs, or after the use of weak 

 NaOH solutions, NaCl, MgS04, LiCl, CO2, evaporation, density of sea- 

 water, overcrowding, and maturity of eggs and sperm. 



