Marsh—Structural Abnormalities in Copepoda. 195 
STRUCTURAL ABNORMALITIES IN COPEPODA. 
C. Dwight Marsh. 
With Plate X, figs. 1-6. 
Abnormal or freak structures in the genera of Cyclops and 
Diaptomus are remarkably rare. While there is great variabil¬ 
ity in the species of Cyclops, unusual structures seldom occur. 
In Diaptomus, which shows hardly any variability within 
species limits, freak organs are still more rare. 
Yery few references to such structures are made in the cope- 
pod literature. 
Schauss, 1 1908, p. 195, figures a shortened furcal ramus of 
Cyclops vernalis Pischer, evidently a case of regeneration after 
injury. 
A similar case in Cyclops serrulatus Fischer is mentioned by 
Vosseler 2 in 1889. 
Wolf, 3 1905, pp. 203, and 204, discusses “Regenerationser- 
scheinungen,” and mentions finding two specimens of Cyclops 
serrulatus with one furcal ramus shortened. His case of regen¬ 
eration in the furcal setae of Cyclops fimbriatus seems rather one 
of the instances of telescoping of portions of the setae which has 
been discussed by Schmeil and others, and probably is not the 
result of injury and regeneration. 
Because of the -rarity of abnormal structures it seems best to 
1 Beitrag zur Kenntnis der freilebenden Copepoden und Cladoceren 
der Umgegend von Bonn. Yerhand. Naturhist. Ver. der preuss. 
Rheinland nnd Westfalens. 64 Jahrg. pp. 163-218. 
2 beber' einen Cyclops mit verkriippelter Furka. Archiv. fur Naturge- 
schichte, 55, p. 123, Taf. VI, fig. 16. 
3 Die Fortpflanzungsverhaltnisse unserer einheimischen Copepoden. 
Zool. Jahrb. Abt. f. Syst. Bd. 22, pp. 101-280. 
