456 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
modium of the Labyrinthuleae. Although the term pseudoplasmo- 
dium may thus tend to be misleading, since it may be regarded as 
implying a body physiologically as well as morphologically compar¬ 
able to the plasmodium, it is nevertheless retained for want of a 
better term. 
Finally, I have followed Zopf in characterizing as a net-plasmo- 
dium ’’ the peculiar form of association occurring in the Labyrinthu¬ 
leae, although in Diplophrys stercorea^ the only member of the 
family with which I am familiar, the individuals may not necessarily 
become joined with other individuals through the contact of their 
pseudopodia, but may in some cases remain isolated and distinct. 
As mentioned later in this paper, moreover, the spindle shaped 
individuals of the Labyrinthuleae, in my opinion, do not present 
close resemblances to the amoeboid individuals of the Acrasieae, 
either in their structure or in their peculiar mode of locomotion. 
While it is true that their mode of development is similar in certain 
respects, the structural resemblance between the two groups is con 
fined to the superficial similarity of their fructifications and is proba¬ 
bly not sufficient to warrant placing the Labyrinthuleae between the 
Acrasieae and the Myxomycetes. 
Historical Summary. 
Our knowledge of the Acrasieae is due mainly to the discoveries 
of Brefeld, Cienkowsky, and van Tieghem. Few observers seem 
to have met with these organisms, hence the list of publications 
relating to the group is a short one. The earliest published obser¬ 
vation of any of the Acrasieae, so far as I am aware, is that of 
Coemans in 1863. Without doubt the form which he figures and 
describes as a pycnidial condition of Rhizopus was one of the com¬ 
moner species of Dictyostelium. Twm other writers, Sorokin and 
Oudemans, misled by superficial resemblances, have made the mis¬ 
take of placing Dictyostelium among the Hyphomycetes. 
Brefeld (’69) was the first to interpret aright the true nature of 
one of these peculiar organisms; he misconstrued at first, however, 
certain details of the life history of his Dictyostelium, in regarding 
the piled up colony of myxamoebae as a fused mass, which he 
described as forming a plasmodium. Rostafinski (’75), therefore, in 
