
REVIEWS. 663 
new species. The second part is **On the Young Stages of Echini." 
'The collections of Count Pourtales included many very young specimens. 
With these Mr. Agassiz has been able to study the young of thirty odd 
different species belonging to*as many different genera. These observa- 
o 
has arrived and the direction in which his labors are likely to affect the 
received ideas of the "leMona of the Echini amongst thems elves. 


than to place the me extremes ni tl i t only in diff t species, but often in different 
genera, and even in different famil 
The diffe rni stages of vitem of Toxopneustes drobachiensis Ag., rep- 
resent in the younger stages nd then Hemicidaris, then esie 
adema, Echinocidaris, and Heliocidari 
In Cidaris, Diadema, and i. the changes are less marked, and in 
Echinometra they are greater than in any other genus of the regular 
Echini 
e is frequently find specimens « the same size, where in one cage the outline is almost 

cone high, surmou nted by numerous short stout spines, 
Among the Clypeastroids we find in the young during their growth great changes of form 
and structure taking place.” 
The transformations of Mellita testudinata and Encope emarginata are 
described as identical, whilst those of Mellita testudinata and Mellita hex 
pora are not so much siena hepa both of the "— genus. 
se The development of Stolono ostratus, and flat Clypeastroids of the type of Cly- 
ene to show that in "connection with mhe develop- 


ment of the Scutellidæ ab described p y p Z 
ti T ti Seu yis na, Runa. Echinocvamus 
hich may eventually prove to be nothing but the young of other .Clypeastro: ed ay Heia, 
Mawes Laganum, Stolonoclypus, ed ova Encope, an tes the like; but want of suffic’ 
material p reve; ents me from eit into this oom parison re in detail. D. we ee 
thr h phases which cannot be 
disti Moulinsia Fibularia, Runa, Scutellina, ond. the Ciypeastroids proper pass, 
as I shall show bel th 1 Echinocyamu 
“The develo’ ment d light the affinities of the 
toothless porera and of f the Cassidulide. It shows conclusively that Echinoneus is only a 
permanent em onie stage of ( Echinolampas, thus 3 becoming allied to me Cant 





2. 

the Lr matak with teeth.” 
E rt of the work is full of important observations giving detailed 
Fiir eg of the development of the species ` dd ort of the general 
propositions a few of which we have quoted ab 
Part No. III. is on their Bathymetrical and Egip Distribution. 
Here Mr. Agassiz reaches a most important and interesting conclusion. 
He concludes, from a specimen of Ananchytes, probably pane ge radi- 
ata found on the Isthmus of Panama, that the Pacific and Gulf of Mexico 
ratin, 
first the deep sea Cretaceous forms, then those of the next zone, which 
Mr. Agassiz says are ‘‘representatively of Tertiary genera,” and finall 
dividing the littoral species. which are now represented by numerous 
