Page "Chlorarachniophyte" Paragraph 1

The chloroplasts were presumably acquired by ingesting some green alga.

They are surrounded by four membranes, the outermost of which is continuous with the endoplasmic reticulum, and contain a small nucleomorph between the middle two, which is a remnant of the alga's nucleus.

This contains a small amount of DNA and divides without forming a mitotic spindle.

The origin of the chloroplasts from green algae is supported by their pigmentation, which includes chlorophylls a and b, and by genetic similarities.

The only other group of algae that contain nucleomorphs are the cryptomonads, but their chloroplasts seem to be derived from a red alga.