A Cytological Study of the Seiiii-parasitic Copepod, Hersilia apodiforinis etc. 435 



IV. Notodelphyoida. 



Observations in tliis group are very incomplete. The author has 

 studied the testes of Notodelphys, Notopterophorus, and Doropygus. The 

 structure of the testes and the form of the germinal elements are practi- 

 cally the same in all three. The "Keimpolster" is located within the 

 blind end of the testis itself (as in Canthocamptus; Haecker '95 a) and 

 is surrounded by spermatogonia, and these spermatogonia contain an 

 immense nucleolus. The cells are small and the ehromosomes of the 

 maturation divisions very difficult to eount. 



VI. Caligoida. 



„ , . , o ( of equal.size; rinsr-form; parallel lods before 



randarus simiatus . . . 8 < . ' . , , ,r ^ 



[ spindle IS lormed. McC. 



Orthagoriscola mvricata . 8 like Pandarus. McC. 



/\';-6j/e;i'a(?)(aDichelestid) 8 ring shaped. McC. 



Mytilicola iniestinaUs , . 8 in primary spermatocytes. S. 



The figures and descriptions of the ehromosomes of the types 

 studied in the Caligoida allow of no generalizations. It is, however, 

 worthy of note that the number eight is common to all the forms so 

 far ihvcstigated. 



Groups V and VII have not been worked upon from a cytological 

 Standpoint. 



E. The Hetero-chromosomes and a Gase of Hermaphroditism. 

 On a slide of sections comprising a series of about forty males of 

 Hersilia apodiformis, there was one individual cut sagittally which was 

 very striking on account of the structure of the sexglands. Closer ex- 

 amination proved the individual to be hermaphroditic. This, so far as the 

 author has been able to ascertain, is the first case of intermal hermaphro- 

 cütism found in the Copepods. Unfortunately this specimen was not 

 carefuUy examined before sectioning, but was included with ordinary 

 males which were always distinguished and separated from the immature 

 females iinder low-power magnification. Its size is that of an ordinary 

 male, and it possesses the large highly modified second maxiUipeds so 

 characteristic of the male (p. 402), and used in holding fast to the female. 

 The sex gland (Fig. 4, Plate IV) is a combination of testis and ovary. 

 There is a "Keimpolster" like that of the testis, and foUowing this are 

 the spermatogonia or oögonia, none of which show stages of active divi- 

 sion. Then, in close succession, are typical zygotene bouquet stages with 

 nuclear cap and nucleolus, an anaphase plate of a second spermatocyte 

 mitosis, many spermatids and developing spermatozoa; and, in neighboring 



