518 PROCEEDINGS OF THE ACADEMY OF [DeC. , 



swimming, Miiller's larvae were obtained without difficulty. I do not 

 know wherein my methods differed from Wheeler's. He suggested 

 that the water in the laboratory was too warm. However I made no 

 attempt to keep it cool, and in some cases the sun shone directly on the 

 dishes without apparently affecting the eggs. The adult animals 

 however would live for only a few days. After the first day they 

 became very sluggish and their bodies began to break up in a manner 

 similar to that descril^ed by "Wheeler. 



Although I studied the question a good deal, I have never been able 

 to ascertain where the eggs of this polyclad are laid imder natural 

 conditions. The animals w^ere laying throughout the entire simimer 

 from June to September, yet I have never foimd a single capsule except 

 when deposited in my dishes. I have repeatedly searched the interior 

 of the branchial chamber of the whelks in which adult worms were 

 found, but to no avail. I have also examined carefully the shells of 

 these gasteropods, both inside and out, but no eA'idence of egg capsules 

 was found. I found that the worms always laid soon after being 

 removed from the whelk to the dishes of sea water, and it is possible 

 that this is the normal stimulus to egg deposition. If such is the case 

 the adult animals must deposit their eggs on stones or other smooth 

 objects on the bottom. In such a case both adult and young would 

 have to rini the risk of again finding a Sycoti/pus and entering its 

 branchial chamber. The risk seems to be consideral)le, and the number 

 of eggs deposited by an individual is perhaps hardly sufficient to 

 warrant such an hypothesis. 



The early divisions up to the forty-eight- or fifty-cell stage were 

 followed and figured in the living egg. The eggs are rather opaque 

 and it is difficult to iDe certain concerning many of the divisions. This 

 whole portion of the cell lineage was later gone over in the stained 

 preparations and the previous observations on the living material 

 were verified or corrected. 



Eggs were fixed in various solutions, among which were sublimate 

 acetic both ac[ueous and in 95 per cent, alcohol, Gilson's murcuro- 

 nitric, picro-sulphuric, picro-acetic, Perenney's fluid and Flemming's 

 solution. Of these the sublimate-acetic mixtures and Gilson's fluid 

 proved most valuable. For staining whole mounts Conklin's (02) 

 picro-hannatoxlyn was used. Slightly stronger hsematoxlyn than 

 reconniiended by Conklin was found better for these particular eggs. 

 The eggs were then cleared in xylol and mounted in balsam. It was 

 impossible on account of their small size to remove the eggs from the 

 capsules, but it was found that they cleared better if the capsules were 

 torn into small pieces. 



