304 Mr. H. M. Bernard on 



causes which result in different ultimate products are mainly 

 physiological. 



Confining our attention entirely to Crustacea, eggs and 

 sperm have been frequently found developing in the same 

 gland. Nebeski * found that in Orchestia the sperm develops 

 in the posterior end of the gland, eggs in the anterior. In a 

 Decapod — Gebia major — all the males examined by Ishikawaf 

 had eggs developing in the posterior end of the gland. 

 Rudimentary eggs have been found in the testis of a Crayfish, 

 and the process of the formation of these eggs out of the 

 same cells, which elsewhere normally form sperm, has been 

 followed out in detail \. This is also insisted upon by 

 Moore in the paper above quoted with reference to Dranchipus. 

 Hermaphrodite individuals are said not to be uncommon 

 among the parthenogenetic Cladocera, appearing about the 

 same time as the males. To this I shall have to refer 

 again §. In the face of these records it is difficult to see 

 why there should be any special improbability in sperm-cells 

 occasionally appearing along with eggs in the long, branched, 

 and apparently but little differentiated genital glands of the 

 Apodidas, a family, be it remembered, in which the males, 

 in several species at least, are very rare. 



My experience, however, shows more than this. The 

 specimens from high latitudes, containing a rather large 

 L. glacialis from Greenland and several specimens of the 

 minute L. spitzberyensis, show one particular portion of the 

 reproductive gland apparently normally transformed into a 

 sperm-forming region, while the rest produces eggs. These 

 arctic dwellers are perhaps arrested rather early in their 

 development ||. The posterior end of the genital gland 

 does not grow out into rich branchings, but tapers off 



* " Beitrage zur Kenntniss der Ampliipoden der Adria," Arb. Zool. 

 Inst. Wien, vol. iii. 1880, p. 24. 



t Zool. Anz. xiv. 1891, p. 70. 



X La V alette St. George, " Innere Zwitterbildung beim Flusskrebs," 

 Arch. mikr. Anat. Bd. xxxix. 1892, p. 504. 



§ In addition to these, the well-known cases of the Cirripedes and of 

 certain Isopods may be cited. With regard to the latter, cf. Bullar, 

 Joum. of Anat. and Physiol, xi. 1876, p. 118 ; Mayer, Mitth. aus der zool. 

 Stat. Neapel, Bd. i. 1879, p. 165 ; Leichman, Bibliotheca Zool. Bd. iii. 

 Heft x. 1891. 



|| As they were caught in large numbers by Prof. Kiikenthal and the 

 late Dr. Alfred Walter a week or two before the arctic winter set in, it is 

 impossible to consider the specimens as immature. According to 

 Dr. A. S. Packard (" North-American Phyllopod Crustacea," U.S. Geol. 

 and Geogr. Surv. 12th Ann. Rep. 1883) 14 millim. was the average size 

 of his specimens of L. glacialis, which were nevertheless adults— that is, 

 if we may judge from the size of their tail-plates. 



