328 JOHN \V. SCOTT. 



depositing eggs or sperm in the laboratory and I studied espe- 

 cially the manner of depositing the eggs. 



My results in general are as follows. First, the egg-laying 

 reflex is closely associated with the time of spring tide, the 

 height of the season occurring at the time of new or full moon, 

 or within two days after these dates. The best results were 

 obtained in July, i. c., a larger percentage of mature worms may 

 be collected during this month than during any other. In early 

 summer the period of sexual activity tends to occur a day or so 

 later than the time mentioned, while in late summer the period 

 tends to be earlier by the same amount. In regard to the second 

 question I may say that the ripe and unripe products are not 

 kept separate in laying with absolute exactness. Though among 

 the first few hundred eggs deposited it is hard to find even one 

 that is immature, toward the close of any given period of ovi- 

 position the immature eggs form a considerable percentage of 

 the total number. But how does the worm keep these eggs 

 apart in the first part of the period ? A full consideration of this 

 question is given later. 



In order to understand the discussion of the two questions 

 concerned it will first be necessary to say something of the habi- 

 tat of this form and the environment under which it lives. 

 These worms live in U-shaped, rather tough, mud tubes that 

 break easily in digging. At one of the openings of the tube, 

 sometimes at both, there is a volcano-shaped mound of sand or 

 earth. The two openings are ordinarily from ten to eighteen 

 inches apart and the depth of the lowest part of the tube is about 

 three fourths the distance between the openings. The worms 

 were collected in six different localities in the vicinity of Woods 

 Hole. In these localities at the time of spring tide extreme 

 high water and extreme low water differ by two to three feet. 

 The tubes are found most abundantly on sandy flats which may 

 vary from fine sand to a rocky character ; they are also occasion- 

 ally formed on sandy mud flats where the tide produces little 

 current. The vertical distribution of the tubes is also compara- 

 tively limited. At the time of extreme low water tubes are 

 rarely found beyond a depth of twelve or fifteen inches, and 

 very few are found more than twelve inches above this line. 



