THE ANATOMY OF PENTACEROS RETICULATUS. 



By D. H. Tennent and V. H. Keiller. 



The following account does not presume to be a complete description 

 of the anatomy of Pentaceros reticulatus. Its chief value lies in the 

 figures which are used in its illustration. 



During my stay at Tortugas in 1909 I made some use of Pentaceros 

 eggs and sperm in experimental work and noted, in making the dissec- 

 tions necessary for obtaining these products, some points in the anatomy 

 which were of unusual interest. These were concerned with the organs 

 of reproduction and with the intestinal caeca. 



I preserved a number of these starfish and sent them to Bryn Mawr, 

 where I suggested to one of my students. Miss V. H. Keiller, that she 

 make a study and careful drawings of their structure. Although done 

 under my supervision, full credit for the work must be given Miss Keiller. 

 During the summer of 19 10 I again examined fresh material as the basis 

 for this account and in order to make sure that none of the structures 

 shown in the drawings were due to the effect of preservation. 



Pentaceros reticulatus (Linck, Linnaeus) is the common West Indian 

 starfish which is so famihar in the dried form in which it is exhibited 

 as a curio in the sea-shore shops. Linck (1733) in his "De stelHs mari- 

 nis" gives two figures of Pentaceros reticulatus, an aboral view on his 

 plate 41 and an oral view on plate 42. 



Miiller and Troschel (1842) use the generic name Oreaster instead of 

 Pentaceros. Perrier (1875) and later systematists have accepted the 

 Linnaean and pre-Linnsean name. Agassiz (1877) and Viguier (1878) 

 have contributed to our knowledge of the skeleton of this form, Agassiz's 

 plate XVI, figs. I, 2, 4, and 5, and Viguier 's plate x, figs. 4 and 5, giving 

 excellent representations of the hard parts of the body. 



Clark (1901, p. 237) notes for this species an observation by Mr. 

 George Gray, of the Marine Biological Laboratory at Woods Hole, "that 

 there are two well-marked varieties of this starfish, so different from 

 each other that, were connecting links wanting, they would easily pass 

 for distinct species. One has the rays acuminate, the disk very high, 

 the skeleton comparatively light, and the oral surface quite spiny, 

 while the other has the rays shorter and more rounded, the disk lower, 

 the skeleton very solid and covered with large tubercles; oral surface 

 more granular and less spiny." 



Studer (1880, p. 545) mentions differences in the color and form of 

 Pentaceros turritus Linck and correlates these with sex. With Penta- 

 ceros reticulatus, although I was able to verify the observation made by 

 Clark, I could not_^convince myself that these were sexual differences. 

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