m. 646] SHORTER ARTICLES AND DISCUSSION 475 



The history of the others shows that the first female with ripe 

 eggs appeared June 5. She was discovered slowly crawling 

 around the dish near the surface of the water. In color and in 

 form this animal resembled the females collected during the 

 breeding season. In size she was rather below the average and 

 somewhat more sluggish. The eggs in size, color and form were 

 identical with the eggs got from animals captured during the 

 breeding season. Subsequently, mature females were found at 

 intervals through the summer. No males appeared until late in 

 June. Eventually, thirty-two females and twelve males fully 

 mature were got from this 1920 culture. 



Males got from the sea copulate with females reared in the 

 laboratory ; such females lay normal eggs that give rise to larv© 

 of a high degree of viability. Males reared in the laboratory 

 copulate with females taken from the sea. The eggs are perfectly 

 normal. On only one occasion did I find a male and female from 

 this 1920 culture sexually mature at the same time. They copu- 

 lated in normal fashion. The eggs laid were normal in every 

 respect and gave rise to larva? that I kept for two weeks before 

 discarding. These larva? could not be distinguished from larvae 

 resulting from eggs laid by animals taken from the sea. 



The 1921 Culture.— At this writing only two mature animals 

 (females) have appeared— one :\Iay 1 aiul on.. May 6, 1922.^ 



The Bate of Growth 

 Some idea of the rate of growtli in these worms may be ob- 

 tained from data collected from the 1913 culture. This was the 

 only culture on which I had the opportunity to make continuous 

 observations. 



Life History 



Observations so far made on culture^ of riattjncreis meqalops 

 reared in the laboratory from eggs laid by animals taken from 

 the sea do not reveal any indieanon of a scxuallv mature inter- 

 mediate form So far, all eg«r. ol.iaiii .1 .i|)p.Mr t > W identical 

 wuth those got from animals in iiatinv. Tins would seem to Mjg- 

 g(Nt that the life hl^tor^ of I'lat >n>' > ' >^ > Minplc \Mihout the 



