372 EDWARD S. MORSE ON 



The nearest approach to these organs has been described by Schulgin in Cistella. He 

 says, "Argiope [= Cistella] has not far from the mouth, on the integument an accumula- 

 tion of cells which play the part of an organ of sense. This organ consists of two longish 

 heaps of cells lying parallel to one another, of which that lying nearer the mouth is 

 formed of specific cells and that farther away from it of epithelial cells." Schulgin figures 

 these organs as projecting from the coelomic wall and describes them as one Tljove 

 another in a median line. He makes no remark about their relation to the external 

 openings of the nephridia, yet there would seem to be some relation between these bodies 

 he describes and the external srlands. 



Early Stages. 



In the previous pages, reference has often been made to the early stages of the shell 

 and the soft parts of these animals; there are other features to be briefly alluded to, 

 however, and in plate 61 I have brought together a number of outlines of the early and 

 nepionic stages of various forms for purposes of comparison. The illumination which 

 Beecher ('92) has shed upon the phylogeny of the Brachiopoda from what little we yet 

 know of the ontogeny, has been based upon material of this kind. In this study he has 

 found a confirmation of certain principles of evolution first enunciated by the lamented 

 Hyatt. In the plate above referred to, I have taken the liberty of reproducing for con- 

 venience of comparison four outlines of the early stages of Terebratulina from my Embry- 

 ology of that species. In 61 : 1 is represented the posterior portion of the shell of an 

 undescribed Lingula from Nagasaki. I made only the briefest observation of the animal, 

 and have no idea of the meaning of the structure outlined within. The nepionic outline 

 with the straight posterior margin is similar to that seen in L. lepidula (42 : 3, 4) , except 

 that it is somewhat broader. In D. lamellosa, at an early stage, the bases of the oblique 

 muscles are slightly flaring, a feature not seen in maturity. In a very early stage (61 : ll) , 

 tliese muscles are excessively flaring at their point of attachment. In a stage where the 

 brachia are well formed, numbering thirty or more cirri, the various muscles may be 

 clearly defined, except that the separation of the anterior occlusor into two muscles ii not 

 apparent though the lateralis is well developed. The anterior and posterior occlusors are 

 compacted within a short space. In 60 : 10, a supernumerary muscle, apparently a repetition 

 of the obliquus posterior, is shown on the right side. Blochmann has figured, in an adult 

 specimen, the same anomaly on the left side. The disproportionate size of the anterior and 

 posterior setae in the young is well shown in the drawings. The nepionic shell (61: ll) is 

 absolutely circular; in this figure the few cirri, seven or eight in ninnber, are turned 

 towards the mouth. The coelomic wall shows distinctly two sets of muscles crossing each 



