MEMOIES OF THE NATIONAL ACADEMY OE SCIENCES. 103 



Phoronis architecta lives at about low-water mark on the sand shoals, which are very 

 numerous in Beaufort Harbor, and, as a rule, the individuals occur in patches. Three or four 

 hundred specimens are often found within a radius of 4 or 5 feet, bul one is very apt to find 

 isolated specimens while digging in the sand anywhere in the harbor. 



( >nl\ rarely do the tubes project a hove the surface of the sand as Andrews ( 1) has described, 

 and in these cases the condition was due to disturbances of the surface of the sand, such as 

 hollows made by Oallinectes. Usually the upper end of the tube is from 3 to 5 cm. below the 

 surface of the sand. 



The average length of these tubes is 13 cm., and the average width a little over 1 mm. The 

 adult when removed from its tube is about 1 mm. in diameter in the posterior one-third, and 

 slightly less in the anterior two-thirds (fig. 61 ). The length of specimens taken out of the tubes 

 varies with the amount of contraction from 20 to 25 mm., which figures are considerably lower 

 than the length given by Andrews (about 50 mm.). The specimens which Andrews described 

 must have been considerably more extended than any we have preserved. When the animal is in 

 its natural habitat and undisturbed, however, it is capable of great extension, stretching the whole 

 length of the tube and even considerably farther, so that its lophophoral end may project above 

 the surface of the sand and reach for some considerable distance along its surface. We have not 

 been able to preserve specimens in their extended condition, and they usually contract to from 

 20 to 25 mm. in length. 



The anterior two-thirds of the living specimen has a flesh color, while the posterior one-third 

 i- dark-yellowish red and quite opaque, which is due to the fact that the gonads and blood caeca 

 arc situated in this region. In preserved specimens, the body wall is annulated (fig. 61), but 

 such is not the case probably in the fully extended individual. 



The crown of tentacles is quite simple compared to the crown of tentacles in P. austraMs, 

 P. Jmskii, and P. pacifica. A cross section shows that it is crescentric and that the ends are not 

 spirally coiled (figs. 62. 63, 64). 



Andrews (1) lias given us a description of the principal points in the anatomy of l'h<>r<>nix 

 architecta, which he has undoubtedly made brief because of the resemblance to the anatomy of 

 Phoronis australis as described by Benham. (2). In general our observations agree with those 

 of Andrews, but there are a few points which merit discussion. 



Lophophoral organs. These peculiar organs (fig. 62) have been observed in several different 

 species of Phoronis, and although functions for them have been suggested, the observations do 

 not seem to have extended over a long enough period in the adult life of the worm to warrant a 

 definite statement as to their function. 



The lophophoral organs (tig. 62) lie one on each side of the median line within the concavity 

 of the lophophore. They are outgrowths from the base of the inner row of tentacles, and. in 

 8ome species at least, are quite conspicuous organs, but they do not arise until the Phoronis has 

 reached its adult size. Organs located in the above region have been described for eight species, 

 but the size and shape do not seem to be the same in all. Whether these differences are specific 

 or whether the observations have been made at different periods in the adult life it is hard to 

 say. Lophophoral organs like those present in Phoronis architt eta arc found in /'. psammophila, 

 P. pacifica, J', rnulleri, and, no doubt, in some other species also. It seems, however, prob- 

 able from the description of the anatomy of P. huskii and /'. <hisir<ilix that in these species 

 the lophophoral organs are much less highly developed than in the smaller species with fewer coils 

 in the lophophoral crown. We have examined several specimens of J', australis with and without 

 genital products, but in no case have we seen organs such as are present in P. architecta. 



Various functions have been assigned t<> the lophophoral organs. Mcintosh (14), working 

 with /'. buskii, considers that they are sensory in function, while Masterman (16), who has studied 

 the same species, says that they are glandular and that they give rise to mucus which serves to 

 hold the embryos together in masses. In other words, he consider- them to be "subsidiary repro- 

 ductive organs." Benham (2), who worked on P. australis, and Cori (4), who investigated 

 /'. psammophila, both give these organs a glandular function, while Andrews (1) thinks that 



