248 
from these two investigators and the two “types” in question left no room 
for doubt of their specific identity. The writer. has since made careful 
study of stained whole-mounts and of serial sections with a view towards 
a more exact determination of the characters of the species as defined by 
Rudolphi. 
Specimens received from Professor Monticelli collected at Trieste 
by Stossich from Mugil sp?, possess hooks of uniformly smaller average 
size (Pl. XXVIII, Fig. 38, 39) than those collected by Professor Parona 
from Mugil auratus and M. cephalus at Genoa. The differences are not, 
however, great; nor are they discontinuous (Fig. 36, 37). In all instances 
the ranges in size of the various hooks for the two collections overlap. 
This may indicate a slight tendency within this species toward the differ- 
entiation of geographical varieties. Varieties have not, however, become 
definitely enough fixed to warrant an attempt to separate them. In the 
light of this evidence of divergence it seemed worth while to investigate 
typical instances of measurements ascribed to members of this species by 
various writers. Table IV presents data for this comparison. 
TABLE IV 
DATA FROM DESCRIPTIONS OF N. agilis 
(Measurements are in ») 
e 
n |a = a 4 n 
oO [ea 3 |= * oO ° 
| es = Ve csi gt a ag CHAM pn ephaciny © 
RECN Wy 8 | 3 i) fs] a 4 a 
| Sikes ‘a a q 3 fe] o 
| ole WEBB la Sbaee A SO lets oll eae een 
Observers |Date |Locality|°2|S x ‘4 ° ° 7) a Ps s ° 
HSolu'o 3) 13) uw 
Ssiee| 22 | 42/82) 2 | 8 | 2 | eels 
Boles Be. |S atolls =e Waa es off 
| Solso| oa oa| og ra a 3 So] 3 
AZ |Z 4 | 4A 4 A, oy H A Z 
Dujardin,............ 1845 |Toulouse 
and 
Rennes} 3/ 6 110 74 65 PSO ees 43 14 3 
Stossichie. cmavisteny dere URS al a op eh Re ee | si ee oe eel Hie Sl ee Snel lace eae) sadiaaey foe soo 3 
Hamanil,.. ©. cascmacee 1895 i Bale 150 70 E2024) anaes <li is maces PRS 2 
Condorelli............ 1898 |Rome...| 3/| 6 131 85 334 250 36 15 
Porbakewcwetacacinernets 1905 e Bada 362 70 50 20 |200-300 |100-200 | 26 
Wie Cle aie ir elements 1919 |Trieste..| 3 | 6 | 94-106 |41-82 |30-65 |150-250 |185-230 |30-41 |12-15 | 2 
(Monticelli Coll.) 
Vid Cleaviecenewecnstm 1919 |Genoa,..| 3 6 | 94-120 |65-83 |41-71 |180-270 |150-200 |30-41 |12-15 2 
(Parona Coll.) | | 
| 
i 
The cement gland in this species has been very generally misin- 
terpreted. Dujardin, in describing three testes, obviously mistook the 
cement gland for a testis. Stossich made the same error. Hamann 
reported six cement glands, though in fact only a single large syncytial 
