ance of degeneration. This connective tissue be- 

 came less apparent with advancing pregnancy. 



Group V, Lactating Females 



Six specimens were selected measuring from 

 167 to 182 cm iS. longirostris) and one 202 cm (S. 

 attenuata). They had been identified as lactating 

 during dissection at sea. It is a heterogeneous 

 group as judged by uterine size, endometrial his- 

 tology, and the appearance of the corpora albican- 

 tia (Table 6). Some animals must have delivered 

 very recently as evidenced by the marked dispar- 

 ity of uterine horn size, hyperemia, and the recent 

 degenerative changes in the corpus luteum, while 

 others had more equal horns and well-advanced 

 corpora albicantia. No active corpora lutea were 

 present while at least one corpus albicans was 

 found in all specimens. Some corpora albicantia 

 had chronic inflammatory cell infiltration and 

 four ovaries had Graafian follicles maturing at 

 various stages. Stretch marks were present on the 

 uterine serosa and the endometrium had typical 

 involutional changes histologically. Beneath the 

 surface epithelium there was a thin zone of 

 hyalinization in most specimens, while recently 

 delivered animals had prominent, congested ves- 

 sels in myometrium and endometrium. Some of 

 these had hyalinized walls also. In a majority of 

 endometria a mild chronic inflammatory infiltrate 

 was present; one had acute pyometritis. No 

 mitoses or edema was present, the endometria ap- 

 peared "resting." Hemosiderin-laden mac- 

 rophages in endometrium or lower uterine seg- 

 ment were present in three, presumably due to 

 interstitial hemorrhage at recent delivery. Such 

 deposits were found in only one other female (Con- 

 trol Group II) whom we suspect to have delivered 

 recently but who was not recorded as lactating. 



FISHERY BULLETIN: VOL. 78, NO. 2 



Experimental Groups 



Group VI, Nonpregnant Animals 

 With Corpus Luteum 



The 58 animals of this group were not detected 

 to be pregnant at sea but had a corpus luteum 

 present in one of their ovaries. The group is di- 

 vided into three subgroups made up of specimens 

 with corpora lutea at different stages of develop- 

 ment or involution. 



GROUP Via.— These 28 animals (19 S. lon- 

 girostris; 9 S. attenuata) measured 163-191 cm in 

 length, and the group was of special importance 

 because the corpora lutea were judged to be the 

 youngest. For this reason, an early pregnancy 

 could have been overlooked. Two intact uteri were 

 dissected meticulously, including the fallopian 

 tubes. Neither embryos nor placentas were iden- 

 tified in any of the 28 specimens. From the dates of 

 capture (Table 7) it will be noted that most (17) 

 were captured in February, as is also true of early 

 pregnant animals (Table 4). These figures must be 

 interpreted with caution, however, because of dif- 

 ferent catch sizes on various cruises. The macro- 

 scopic findings were not uniform in that uterine 

 weight varied between 90 and 467 g, the horn sizes 

 varied considerably and endometrium was as 

 often congested or mucus-covered as not. Only 

 once was the corpus luteum found in the right 

 ovary. 



The histologic appearance of the endometrium 

 correlated neatly with the corpus luteum devel- 

 opment and grouping was undertaken accord- 

 ingly. Those specimens whose corpus luteum had a 

 central fibrin-filled cavity were placed into Group 

 Via; those whose cavity was replaced by fibrous 

 tissue were adjudged to have ovulated earlier and 



Table 6. — Group V: Lactating controls. Specimen no. 1-10 Stenella longirostris; no. 11 S. attenuata. 



518 



