Chromosomes of Eniwetok Opisthobranchiates — Burch and Natarajan 
255 
TABLE 3 
Chromosome Numbers of Opisthobranchs Observed in This Study 
SPECIES 
CHROMOSOME 
NUMBER (n) 
NUMBER OF 
SPECIMENS GIVING 
RESULTS 
NUDIBRANCHIA 
Dendrodorididae 
Dendrodoris nigra 
13 
5 
Favorinidae 
Herviella mietta 
13 (2n= 26) 
1 
ANASPIDEA 
Aplysiidae 
Dolabrifera dolabrifera 
17 
9 
Stylocheilus longicauda 
17 
2 
CEPHALASPIDEA 
Atyidae 
Haminoea linda 
17 
1 
H amino e a mu sett a 
17 
2 
Smaragdinellidae 
Lathophthalmus smaragdinus 
18 
2 
Smaragdinella calyculata 
18 
2 
SOLEOLIFERA 
Onchidiidae 
Onchidella evelinae 
18 
2 
Sowerby) (Fig. 8). In lagoon at north end of 
Eniwetok Island. 
SOLEOLIFERA 
9. Onchidella evelinae Marcus and Burch 
(Fig. 9). In cracks in coral slabs above water 
line (at low tide) on the lagoon side at the 
north end of Eniwetok Island. April 5, I960. 
The materials examined consisted of ovo- 
testes fixed in either Newcomer’s (1953) or 
Carnoy’s (1887) fluids, or the fixative of San- 
felice (1918). The material fixed in New- 
comer’s or Carnoy’s fluids was stained by the 
acetic-orcein squash technique (La Cour, 1941), 
and reproductive tissues fixed in Sanfelice’s 
fluid were sectioned at either 8 or 10 micra and 
stained with Newton’s (1926) crystal violet. 
All observations were made on meiotic cells of 
spermatogenesis (except in Herviella mietta , 
where spermatogonial cells were also studied) 
with a Nikon (Nippon Kogaku) microscope 
equipped with a 100X (n.a. 1.25) oil immer- 
sion objective and 10X, 20 X, and 30 X ocu- 
lars. Drawings were made with the aid of a 
camera lucida and reproduced at a table-top 
magnification of 4260X- 
OBSERVATIONS 
1. Dendrodoris nigra (Fig. 10). The five 
individuals of this species on which we were 
able to obtain satisfactory observations all had 
1 3 bivalents during prophase of the first meiotic 
division. 
2. Herviella mietta (Fig. 11). Only one 
specimen of this species gave satisfactory results. 
It had 13 bivalents during diakinesis and 26 
chromosomes during metaphase in spermato- 
gonial cells. 
3. Dolabrifera dolabrijera (Figs. 12 and 
13). Nine specimens had meiotic cells that 
were satisfactory for chromosome number de- 
terminations. All had 17 bivalents during Pro- 
phase I and Metaphase I. The chromosomes of 
a cell during diakinesis from an acetic-orcein 
squash preparation are shown in Figure 12. 
Metaphase I bivalents from a cell of paraffin 
sectioned material are shown in Figure 13. 
