ENTOMOSTRACA OF MINNESOTA. 143 
Limnosida 
Sig Pseudosid. __-Latona 
Holopedidz ve ee ape San 
She: ‘\ Daphnella 
a 2 ‘F 
Sal 
(SIDIDZ) 
Simocephalus 
I on mee 
(?) -~-~---- oa n--- MOINA----Ceriodaphnia ‘Daphnia 
7 I vN / 
Hi \S . ‘ a . 
we <LYNCO DAPHNIDA. > ‘ Scapholeheris 
oa | “N SS 
va y MN 
PR ae Streblocercus Macr othrix ~ Lyncodaphnia 
osmina y Se ' 
/ | ESS : 
Lathonura = Orepanothrik ~~ e =e Soe 
-< 
/Hocryptus 
! 
' 
Acantholeberis 4 LY NC EIDA » 
1 
| Leydidia 
Furycercus: © ~ 7° 
Camptocercus______7 zk 
Sid 7 ~o 
Alonopsis-~~ Wee artes 
‘\ 
(Alona) +7 a 
Lynceus Graptolebris 
ff Pletroxus), 
s ‘\ 
Chydorts ae 
XN 
‘Monospilus 
part of the body, or at least forms a sac for the protection of the eggs. 
This so called shell springs as a fold from the maxillary segment, and 
is the most conspicuous and variously formed, while really least im- 
portant, of the structural peculiarities. 
All Cladocera begin life with a single median eye, but some lose it 
during later life. In one case it remains the only visual organ. 
The outer covering is in most cases changed by frequent moults. 
The period of the moult is one of the most precarious in the life his- 
tory of the animal. 
Although figures and brief descriptions of animals belonging to 
this group are to be found in the works of Swammerdam, Leuwen- 
hoek, Trembley and others of the older authors, Mueller* was the 
first to produce a systematic work upon these in common with other 
minute fresh-water crustacea. He may be called the father of the 
study of micro-crustacea. Jurine,f an eminent Swiss naturalist, was 
the next to contribute important discoveries relating to these inter- 
esting animals, though Ramdohr had given anatomical details of sev- 
* Entomostraca, seu Insecta testacea, quie in aquis Danice et Norvegice repcrit descripsit, etc. Otto 
Friedrich Miiller, 1785. 
+ Monoce. qui se trouvent aux Envir. de Geneve. 
