MORGULIS. — DEVELOPMENT OF TOXOPNEUSTES VARIEGATUS. 135 



ings, the numbers indicating the full length of the drawing in milli- 

 meters, and though not giving the actual size of larvae, offer a basis 

 for comparison of the larvae with one another. 



Solutions of atropine and pilocarpine of a very weak concentration 

 (about 1 : 60000) exert no influence whatever upon the developing 

 eggs, neither during the cleavage stages nor later when the larval 

 stage is reached. But with the increase of concentration of those 

 solutions their effects become pronounced, the necessary strength, 

 however, being different for the two reagents. Definite results may 

 be obtained with atropine by adding £ c.c. of a 0.5 per cent aqueous 

 solution to 100 c.c. of sea-water (1 : 40000), while pilocarpine in 

 the same concentration does not produce any noticeable influence. In 

 no case, except when the concentration of the atropine or pilocarpine 

 was strong enough to injure the eggs, has there been any influence 

 produced upon the developing eggs during segmentation; the effect 

 was shown only in stages involving the transformation of the gastrula 

 to a pluteus and in those following it. 



The larvae developing in atropine solutions of the strength indi- 

 cated are invariably smaller than the normal ones. The pilocarpin- 

 ized larvae, when they develop in sea-water to which there has been 

 added from 1 c.c. to 2 c.c. of a 0.5 per cent aqueous solution of pilo- 

 carpine per each 100 c.c. of sea-water (1 : 10000 or 20000), are also 

 smaller than normal ones ; but in weaker solutions, those containing 

 from 0.5 c.c. to 1 c.c. of the 0.5 per cent pilocarpine solution to every 

 100 c.c. of sea- water, the larvae may be either quite normal, so far as 

 size is concerned, or they may vary from the normal, being either 

 slightly larger or slightly smaller. The following two Tables (I, II), 

 presenting the notes of two experiments started at the same time, 

 but with eggs of different animals, well illustrate this point. 



From these tables it will be seen that cleavage is not in the least 

 affected by any of the three different strengths of atropine and pilo- 

 carpine used. But the influence became apparent on the next day, 

 when the surface of the water of control dishes was teaming with plutei, 

 while in atropine the young were still in the gastrula stage, or just begin- 

 ning to change to plutei, and very few were swimming at the surface. 

 It will also be seen that in one case the pilocarpinized embryos are 

 slightly larger than the normal ones, while in the other set of experi- 

 ments they are smaller by just as much. In addition to the fact that 

 the differences in the size-relations of the embryos are quite insignifi- 

 cant, the fact that those differences are not of a constant nature indi- 

 cates that they are chance variations rather than the result of the 

 action of pilocarpine. 



