GEODIA MESOTRIAENA. 



Ill 



February 9, 1889, in 34° 4' N., 120° 19' 30" W., depth 47 m. (26 f.) ; it grew on a 

 bottom of gray sand; the bottom temperature was 12.7° (54.9° F.). 



These three varieties differ in many details. The specimen from Station 

 2909, var. pachana, is meandric and rich in praeoscular cavities, the other two 

 are nearly solid. The rhabdomes of all the three kinds of teloclades, the large 

 choanosomal amphioxes, and the small dermal rhabds, are considerably thinner 

 in var. microana than in the other two. Among the small dermal rhabds styles 

 are frequent in var. pachana but rare in the other two. The average clade- 

 rhabdome angle of the orthoplagiotriaenes is in var. megana 91.9°, in var. 

 pachana, 99.4°, and in var. microana 104.2°. The mesoprotriaene-epirhabds 

 are shorter in var. pachana, the mesoprotriaene-clades longer in var. megana, 

 and the clade-epirhabd angles smaller in var. microana than in the others. 

 The anatriaene-clades are considerably longer and less divergent in var. megana 

 than in the other two, which latter differ from each other by the anatriaene- 

 clades being stout in var. pachana and slender in var. microana. The oxyasters 

 and, to a smaller extent, also the oxysphaerasters are larger in var. inegana 

 than in the other two. The sterrasters are relatively narrower in var. microana 

 than in the other two. 



Since these specimens are all large and apparently full grown, these differ- 

 ences cannot be ascribed to differences in age. Some of them miglit of course 

 be mere individual adaptations or due to differences of germ-separation or mix- 

 ture before or during fertilization; others, however, particularly the cUfferences 

 in the clade-rhabdome angles of the orthoplagiotriaenes, the shape of the dermal 

 rhabds, and the relative breadth of the sterrasters, seem to be germinal in nature 

 and sufficient for varietal distinction. (See table on p. 112.) 



On account of their cribriporal afferents and efferents and their spiculation 

 these sponges belong to Geodia. The only other species with similar spicula- 

 tion, either of this genus or of Sidonops, which I have also compared with 

 Geodia mesotriaena, are G. arabica Carter, G. agassizii, G. mesotriaenella, G. 

 breviana, and G. ovis. 



According to the description and figures given by Carter ' and Topsent ^ 

 the choanosomal euasters of G. arabica are different from those of G. meso- 

 triaena; the megascleres of the former are much smaller than those of the latter, 

 and G. arabica has hitherto been found only in the Red Sea, while G. meso- 

 triaena appears to be confined to the coast of California. G. agassizii has no 



' //. J . Carter. A descriptive account of four subspheious sponges. Ann. mag. nat. hist., 1869, 

 ser. 4,4, p. 4, pi. 1, figs. 13, 1.3a. 



'■' E. Topsent. ^Iponges de la Mer Rouge. Mem. Soc. zool. France, 1892, 5, p. 23. 



