1918 Bovard and Osterud; on Embryological Material 129 



a great many eggs, and more often at night than during the day. The 

 hydroid of this medusa is a tubularian, probably some species of Peri- 

 gonimus. 



Polyorchis minuta Murbach & Shearer. Common in Friday Harbor, 

 and easily obtained from the laboratory floats, June to August. It is never 

 seen in large numbers and is variable from day to day. The eggs are large 

 and clear. It was rather scarce during 1918. The hydroid of this is not 

 known. An attempt should be made to raise these from the eggs. 



Aequorea forshalea Peron and Lesueur. Abundant in Friday Harbor 

 during June, July and August. It is easily obtained almost any day 

 from the laboratory docks. The eggs are large and clear, and the cleavage 

 stages are easily followed. The hydroid is a minute Campanulina. 



Thaumantias cellularia Haeckel. Abundant in Friday Harbor at al- 

 most any time from June to August. They sometimes appear in great 

 numbers, and can be obtained from the Station floats. The eggs are the 

 largest of any among the common medusae found in this vicinity, and are 

 transparent. The hydroid is a Thaumantias. Development of the eggs in 

 the laboratory is difficult since the cleavage stages are very sensitive to any 

 change of conditions. 



Diphyes sp. Occasional specimens were picked up floating by the 

 Station docks. Many were seen during the summer of 1917, a few in 

 1918. Eggs were obtained in 1917, and Mr. M. C. Riddle observed part of 

 their development. 



Haliclystis sp. Common on the eelgrass at False Bay on the west 

 shore of San Juan Island ; occasionally found on eelgrass in Argyle Bay, 

 also near Twin Island. They can be obtained at extreme low tides. De- 

 veloping eggs were secured in 1917 in early August. 



Aurelia sp. Adult specimens are scarce. Two ephyra were casually 

 picked up at the Station floats in 1917 and one in 1918. 



Epiactis prolifera Verrill. Abundant on the eelgrass at low tide in 

 Friday Harbor. This is the only actinian observed to be reproducing. 

 The eggs are large, but opaque with reddish brown yolk. It seems likely 

 that development occurs to an advanced stage within the parent body, and 

 that the young migrate from their position of origin to their conspicuous 

 location outside, attached to the body of the parent in a manner imitative 

 of budding. As all sizes of these young are obtainable all summer the 

 reproductive season is probably quite prolonged. 



Caryophyllia sp. A simple coral common on rocks exposed at low 

 tide on the exposed channel of Turn Island; also on the Sucia Islands. 

 In 1917 swimming larvae thought to be those of Caryophyllia were noticed 

 in a dish in wliich some specimens had been brought into the laboratory. 



Mnemiopsis sp. Common forms easily obtained from Station floats, 



