PHORONIS ARCHITECTA— BROOKS AND COWLES. 77 



seem probable that this is the case for Phoronis architecta, because full-sized adults are found 

 throughout the year in Beaufort Harbor, and specimens were kept alive for fifteen months in the 

 laboratory of Johns Hopkins University. 



THE LAYING OF THE EGGS. 



During low tide in the summer and autumn it was easy to colled from loo to 150 specimens 

 of Phoronis architecta during an hour or two. About one-half of these would usually have 

 male reproductive organs and the rest female reproductive organs. The Phoronis were placed 

 in glass crystallizing dishes and after about twenty-four hours many of the individuals began to 

 lay — usually at night — but the eggs were not retained among the tentacles in a mass, as described 

 by most investigators, but were swept gently away from the lophophoral crown by the ciliation 

 on the tentacles and on the anal region, so that they settled near by on the bottom of the dish. 

 Sometimes, however, the newly laid eggs were carried up and down the tentacles in currents 

 caused by the cilia, and occasionally a few eggs were found grouped near the tips of the tentacles, 

 being held there, loosely by a small quantity of mucus-like material. At no time, however, were 

 eggs and larvse aggregated in definite masses, as described by Ikeda (!*), nor were they brooded 

 among the tentacles, as Masterman (16) has observed in the case of Phoronis huskii. That eggs 

 and embryos were not found by Longchamps among the tentacles of " Phoronis <l Helgoland" is no 

 doubt due to the fact that the same habit prevails in the above form that does in Phoronis 

 architt eta. 



While the adults were laying, they were examined under the compound microscope. They 

 showed large numbers of eggs which were floating freely back and forth in the body cavity as 

 the animal contracted and expanded. Sections of adults in this condition show that all these free 

 eggs contained the first polar body spindle. At intervals of about one minute an egg is extruded 

 with considerable force from the nephridial opening, and in no case do the eggs at this moment 

 have polar bodies. The wall of the nephridial ridge is transparent enough to see the eggs 

 as they slip through the larger part of the nephridium. While passing through, they are 

 pressed by the walls of the organ until they are about twice as long as broad (fig. 1). The fact 

 that Phoronis architecta does not keep its eggs in masses within the tentacular crown, together 

 with the fact that most of the individuals lay them at about the same lime at night, makes 

 it possible to preserve any one stage in the development of the embryo in sufficient quantity for 

 a thorough study. 



FERTILIZATION. 



Ikeda ('.») and Longchamps (12) made the observation that the eggs in the body cavity of the 

 parent showed the spindles of the first polar body. This I found to be the case in Phoronis 

 architecta (tig. 1). Eggs in the nephridia were found to be in the same stage, and in neither case 

 was there any sign of an entering spermatozoon or a male pronucleus (fig. 1). There is no doubt 

 of the fact that in Phoronis architecta the spermatozoon does not enter the egg until the latter 

 has been expelled from the nephridium. Ikeda observed this fact for Phoronis i/jimai. 



SEGMENTATION. 



The eggs of Phoronis architecta while still in the body cavity are somewhat irregular in 

 shape, and. as mentioned above, are decidedly so while passing through the nephridium. 

 However, after they are laid they become almost perfectly spherical and average loo /< in diam- 

 eter (fig. 2), thus measuring the same as the egg of "Phoronis </< X(i]il<*." (Longchamps (12).) 

 The egg is very opaque, being heavily laden with small yolk granules. It is surrounded by a 

 delicate membrane, which, however, is not very conspicuous, being closely applied to the sur- 

 face, but after fertilization it separates to some extent (fig. •!). 



Observations on the segmentation of the egg of Phoronis are conflicting. This part of the 

 development of Phoronis seems to have been treated hastily by most observers, probably 

 because it is difficult to obtain sufficient material for its study. It is agreed that the segmenta- 

 tion is total. Foettinger (5) and E. Schultz (21) claim that the segmentation is unequal. 



