MARCH: GERM CELLS OF CORYMORPHA. 249 



of the medusa bud. Torrey's other papers on Corymorpha* 

 fail to throw any additional light upon the subject of the origin 

 or migration of the germ cells. 



MATERIAL AND TECHNIQUE. 



The material from which these observations were made was 

 collected at Pacific Beach, Calif., during the summer of 1914. 

 Some of the material was fixed in Flemming's fixative, some in 

 Telleyesniczky's fluid, and some in Zenker's. All of these 

 fixatives gave good results, but, on the whole, the Flemming 

 material was most satisfactory. 



At first single medusa? were cut longitudinally and trans- 

 versely, and an attempt was made to isolate and section in a 

 definite plane small pieces of the peduncle, bearing one or two 

 of the younger buds, in hopes of getting all stages of develop- 

 ment, but it has proven more satisfactory to use the whole 

 peduncle with all but the largest medusae attached. By this 

 method there is always the chance of cutting a few of the buds 

 in the proper plane, and the sex of the older medusae serves as 

 a guide to the sex of the younger buds, since medusae of only 

 one sex develop on a single peduncle. 



The sections were all cut four or five micra in thickness. 

 Benda's Mitochondria stain, Rubaschkin's stain, Bensley's 

 neutral gentian stain, and iron-haematoxylin with eosin or 

 Congo red were used in staining the sections. Iron-haema- 

 toxylin with neutral gentian as a counter-stain proved the 

 best for differentiating germ cells, and the combination of 

 these two stains was used for most of the sections. 



I. — FORMATION AND DEVELOPMENT OF THE MEDUSA. 



Young medusae of Corymorpha palma usually develop in 

 groups as outpushings from the stalks of older buds, although 

 they frequently occur singly along the main peduncle. The 

 first indication of the formation of a new bud is a clumping 

 of entodermal cells and a rounding out of the ectoderm in 

 this region (figure 2). At the time of this outpushing 

 the nematocyst cells have practically disappeared from the 

 ectoderm of the bud, while the ectoderm and mesoglea both 

 are noticeably thinner here than in other regions of the 



* Torrey, Harry Beal. 1902. Hydroids of the Pacific Coast of North America. Uni- 

 versity of California Publications. Zoology, Vol. I, No. 1. 



1907. Biological Studies on Corymorpha. I, C. palma and Environment. Journal of 

 Experimental Zoology, Vol. I, No. :!. 



